Method for producing a 3d semiconductor device and structure including power distribution grids

ABSTRACT

A method for producing a 3D semiconductor device: providing a first level with a first single crystal layer; forming control circuitry of first transistors in and/or on the first level with a first metal layer above; forming a second metal layer above the first metal layer; forming a third metal layer above the second metal layer; forming at least one second level on top of or above the third metal layer; performing additional processing steps to form a plurality of second transistors within the second level; forming a fourth and fifth metal layers above second level; a global power distribution grid includes fifth metal, and local power distribution grid includes the second metal layer, where the fifth metal layer thickness is at least 50% greater than the second metal layer thickness.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This application relates to the general field of Integrated Circuit (IC)devices and fabrication methods, and more particularly to multilayer orThree Dimensional Integrated Circuit (3D-IC) devices and fabricationmethods.

2. Discussion of Background Art

Over the past 40 years, there has been a dramatic increase infunctionality and performance of Integrated Circuits (ICs). This haslargely been due to the phenomenon of “scaling”; i.e., component sizeswithin ICs have been reduced (“scaled”) with every successive generationof technology. There are two main classes of components in ComplementaryMetal Oxide Semiconductor (CMOS) ICs, namely transistors and wires. With“scaling”, transistor performance and density typically improve and thishas contributed to the previously-mentioned increases in IC performanceand functionality. However, wires (interconnects) that connect togethertransistors degrade in performance with “scaling”. The situation todayis that wires dominate the performance, functionality and powerconsumption of ICs.

3D stacking of semiconductor devices or chips is one avenue to tacklethe wire issues. By arranging transistors in 3 dimensions instead of 2dimensions (as was the case in the 1990s), the transistors in ICs can beplaced closer to each other. This reduces wire lengths and keeps wiringdelay low.

There are many techniques to construct 3D stacked integrated circuits orchips including:

-   -   Through-silicon via (TSV) technology: Multiple layers of        transistors (with or without wiring levels) can be constructed        separately. Following this, they can be bonded to each other and        connected to each other with through-silicon vias (TSVs).    -   Monolithic 3D technology: With this approach, multiple layers of        transistors and wires can be monolithically constructed. Some        monolithic 3D and 3DIC approaches are described in U.S. Pat.        Nos. 8,273,610, 8,298,875, 8,362,482, 8,378,715, 8,379,458,        8,450,804, 8,557,632, 8,574,929, 8,581,349, 8,642,416,        8,669,778, 8,674,470, 8,687,399, 8,742,476, 8,803,206,        8,836,073, 8,902,663, 8,994,404, 9,023,688, 9,029,173,        9,030,858, 9,117,749, 9,142,553, 9,219,005, 9,385,058,        9,406,670, 9,460,978, 9,509,313, 9,640,531, 9,691,760,        9,711,407, 9,721,927, 9,799,761, 9,871,034, 9,953,870,        9,953,994, 10,014,292, 10,014,318, 10,515,981, 10,892,016; and        pending U.S. Patent Application Publications and applications,        Ser. Nos. 14/642,724, 15/150,395, 15/173,686, 16/337,665,        16/558,304, 16/649,660, 16/836,659, 17/151,867, 62/651,722;        62/681,249, 62/713,345, 62/770,751, 62/952,222, 62/824,288,        63/075,067, 63/091,307, 63/115,000, 63/220,443, 2021/0242189,        2020/0013791, 16/558,304; and PCT Applications (and        Publications): PCT/US2010/052093, PCT/US2011/042071        (WO2012/015550), PCT/US2016/52726 (WO2017053329),        PCT/US2017/052359 (WO2018/071143), PCT/US2018/016759        (WO2018144957), PCT/US2018/52332 (WO 2019/060798), and        PCT/US2021/44110. The entire contents of all of the foregoing        patents, publications, and applications are incorporated herein        by reference.    -   Electro-Optics: There is also work done for integrated        monolithic 3D including layers of different crystals, such as        U.S. Pat. Nos. 8,283,215, 8,163,581, 8,753,913, 8,823,122,        9,197,804, 9,419,031, 9,941,319, 10,679,977, 10,943,934,        10,998,374, 11,063,071, and 11,133,344. The entire contents of        all of the foregoing patents, publications, and applications are        incorporated herein by reference.

Regardless of the technique used to construct 3D stacked integratedcircuits or chips, heat removal is a serious issue for this technology.For example, when a layer of circuits with power density P is stackedatop another layer with power density P, the net power density is 2P.Removing the heat produced due to this power density is a significantchallenge. In addition, many heat producing regions in 3D stackedintegrated circuits or chips have a high thermal resistance to the heatsink, and this makes heat removal even more difficult.

Several solutions have been proposed to tackle this issue of heatremoval in 3D stacked integrated circuits and chips. These are describedin the following paragraphs.

Publications have suggested passing liquid coolant through multipledevice layers of a 3D-IC to remove heat. This is described in“Microchannel Cooled 3D Integrated Systems”, Proc. Intl. InterconnectTechnology Conference, 2008 by D. C. Sekar, et al., and “ForcedConvective Interlayer Cooling in Vertically Integrated Packages,” Proc.Intersoc. Conference on Thermal Management (ITHERM), 2008 by T.Brunschweiler, et al.

Thermal vias have been suggested as techniques to transfer heat fromstacked device layers to the heat sink. Use of power and ground vias forthermal conduction in 3D-ICs has also been suggested. These techniquesare described in “Allocating Power Ground Vias in 3D ICs forSimultaneous Power and Thermal Integrity” ACM Transactions on DesignAutomation of Electronic Systems (TODAES), May 2009 by Hao Yu, Joanna Hoand Lei He.

Other techniques to remove heat from 3D Integrated Circuits and Chipswill be beneficial.

Additionally the 3D technology according to some embodiments of theinvention may enable some very innovative IC alternatives with reduceddevelopment costs, increased yield, and other illustrative benefits.

SUMMARY

The invention may be directed to multilayer or Three-DimensionalIntegrated Circuit (3D IC) devices, structures, and fabrication methods.

In one aspect, a 3D semiconductor device, the device including: a firstlevel, where the first level includes a first layer, the first layerincluding first transistors, and where the first level includes a secondlayer, the second layer including first interconnections; a second leveloverlaying the first level, where the second level includes a thirdlayer, the third layer including second transistors, and where thesecond level includes a fourth layer, the fourth layer including secondinterconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, where the second level includes at least one RadioFrequency circuit; and a shielding layer disposed between the RadioFrequency circuit and the second layer.

In another aspect, a 3D semiconductor device, the device including: afirst level, wherein said first level comprises a first layer, saidfirst layer comprising first transistors, and wherein said first levelcomprises a second layer, said second layer comprising firstinterconnections; a second level overlaying said first level, whereinsaid second level comprises a third layer, said third layer comprisingsecond transistors, and wherein said second level comprises a fourthlayer, said fourth layer comprising second interconnections; and aplurality of connection paths, wherein said plurality of connectionpaths provides connections from a plurality of said first transistors toa plurality of said second transistors, wherein said second level isbonded to said first level, wherein said bonded comprises oxide to oxidebond regions, wherein said bonded comprises metal to metal bond regions,wherein said second transistors comprise a first second transistor and asecond second transistor, wherein said first second transistor has atleast two side gates and has a first threshold voltage (Vt), whereinsaid second second transistor has at least two side gates and has asecond threshold voltage (Vt), and wherein said first threshold voltageis different from said second threshold voltage by at least 30%.

In another aspect, a 3D semiconductor device, the device including: afirst level, wherein said first level comprises a first layer, saidfirst layer comprising first transistors, and wherein said first levelcomprises a second layer, said second layer comprising firstinterconnections; a second level overlaying said first level, whereinsaid second level comprises a third layer, said third layer comprisingsecond transistors, and wherein said second level comprises a fourthlayer, said fourth layer comprising second interconnections; and aplurality of connection paths, wherein said plurality of connectionpaths provides connections from a plurality of said first transistors toa plurality of said second transistors, wherein said second level isbonded to said first level, wherein said bonded comprises oxide to oxidebond regions, wherein said bonded comprises metal to metal bond regions,wherein said second level comprises at least one first ElectroStaticDischarge (ESD) circuit, and wherein said first level comprises at leastone second ElectroStatic Discharge (ESD) circuit.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, where the second level includes at least one Electrostaticdischarge (ESD) circuit.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, where the second level includes a rectangular guard-ringstructure, and where the second transistors and the secondinterconnections are surrounded by the guard-ring structure.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, where the first level includes first dice lines, where thesecond level include second dice lines, and where the second dice linesare aligned to the first dice lines with less than 1 micron alignmenterror.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where the first level includes a plurality of trenchcapacitors.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where the second level includes an antenna adapted forwireless communication.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where at least one of the second transistors channelincludes non-silicon atoms.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where the device includes a plurality of capacitors.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where the second level includes Radio Frequency (RF)circuits adapted for data communication.

In another aspect, a 3D semiconductor device, the device including: afirst level, where the first level includes a first layer, the firstlayer including first transistors, and where the first level includes asecond layer, the second layer including first interconnections; asecond level overlaying the first level, where the second level includesa third layer, the third layer including second transistors, and wherethe second level includes a fourth layer, the fourth layer includingsecond interconnections; and a plurality of connection paths, where theplurality of connection paths provides connections from a plurality ofthe first transistors to a plurality of the second transistors, wherethe second level is bonded to the first level, where the bonded includesoxide to oxide bond regions, where the bonded includes metal to metalbond regions, and where at least one of the first transistors includes atransistor channel, the transistor channel including at least 1%non-silicon atoms.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming control circuitry in and/or on thefirst level, where the control circuitry includes first single crystaltransistors; forming a first metal layer above the first single crystallayer; forming a second metal layer above the first metal layer; forminga third metal layer above the second metal layer; forming at least onesecond level disposed on top of or above the third metal layer;performing a first etch step; performing additional processing steps toform a plurality of second transistors within the at least one secondlevel; forming a fourth metal layer above the at least one second level;forming a fifth metal layer above the fourth metal layer, where thefifth metal layer is aligned to the first metal layer with a less than40 nm alignment error, where the device includes a global powerdistribution grid, where the global power distribution grid includes thefifth metal layer, where the device includes a local power distributiongrid, where the local power distribution grid includes the second metallayer, and where the fifth metal layer thickness is at least 50% greaterthan the second metal layer thickness.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming a plurality of first transistors inand/or on the first level; forming a first metal layer above the firstsingle crystal layer; forming a second metal layer above the first metallayer; forming a third metal layer above the second metal layer; formingat least one second level disposed on top of or above the third metallayer; performing a first etch step; performing additional processingsteps to form a plurality of second transistors within the at least onesecond level; forming a fourth metal layer above the at least one secondlevel; forming a connection to the at least one second metal layer,where the connection includes a via through the at least one secondlevel; forming a fifth metal layer above the fourth metal layer, wherethe via includes a radius of less than 450 nm, where the device includesa global power distribution grid, where the global power distributiongrid includes the fifth metal layer, where the device includes a localpower distribution grid, where the local power distribution gridincludes the second metal layer, and where the fifth metal layerthickness is at least 50% greater than the second metal layer thickness.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming a plurality of first transistors inand/or on the first level; forming a first metal layer above the firstsingle crystal layer; forming a second metal layer above the first metallayer; forming a third metal layer above the second metal layer; formingat least one second level disposed on top of or above the third metallayer; performing a first etch step; performing additional processingsteps to form a plurality of second transistors within the at least onesecond level; forming a fourth metal layer above the at least one secondlevel; forming a connection to the second metal layer, where theconnection includes a via through the at least one second level; forminga fifth metal layer above the fourth metal layer, where the via includesa radius of less than 450 nm, where at least one of the plurality ofsecond transistors includes a metal gate, and where the fifth metallayer thickness is at least 50% greater than the second metal layerthickness.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming control circuitry in and/or on thefirst level, where the control circuitry includes first single crystaltransistors; forming a first metal layer above the first single crystallayer; forming a second metal layer above the first metal layer; forminga third metal layer above the second metal layer; forming at least onesecond level disposed on top of or above the third metal layer;performing additional processing steps to form a plurality of secondtransistors within the at least one second level; forming a fourth metallayer above the at least one second level; and forming a fifth metallayer above the fourth metal layer, where the at least one second levelincludes at least one first oxide layer overlaid by a transistor layerand then overlaid by second oxide layer, where a distance from a top ofthe first oxide layer to a bottom of the second oxide layer is less thantwo microns, where the device includes a global power distribution grid,where the global power distribution grid includes the fifth metal layer,where the device includes a local power distribution grid, where thelocal power distribution grid includes the second metal layer, and wherethe fifth metal layer thickness is at least 50% greater than the secondmetal layer thickness.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming a plurality of first transistors inand/or on the first level; forming a first metal layer above the firstsingle crystal layer; forming a second metal layer above the first metallayer; forming a third metal layer above the second metal layer; formingat least one second level disposed on top of or above the third metallayer; performing a first etch step; performing additional processingsteps to form a plurality of second transistors in and/or on the atleast one second level; forming a fourth metal layer above the at leastone second level; forming a connection to the at least one second metallayer from the fourth metal layer, where the at least one second levelincludes at least a first oxide layer overlaid by a transistor layer andoverlaid by a second oxide layer, where the distance from the firstoxide layer to the second oxide layer is less than two microns, wherethe connection includes a via through the at least one second level; andforming a fifth metal layer above the fourth metal layer, where the viaincludes a radius of less than 450 nm, where the device includes aglobal power distribution grid, where the global power distribution gridincludes the fifth metal layer, where the device includes a local powerdistribution grid, where the local power distribution grid includes thesecond metal layer, and where the fifth metal layer thickness is atleast 50% greater than the second metal layer thickness.

In another aspect, a method for producing a 3D semiconductor device, themethod including: providing a first level, the first level including afirst single crystal layer; forming a plurality of first transistors inand/or on the first level; forming a first metal layer above the firstsingle crystal layer; forming a second metal layer above the first metallayer; forming a third metal layer above the second metal layer; formingat least one second level disposed on top of or above the third metallayer; performing additional processing steps to form a plurality ofsecond transistors within the at least one second level; forming afourth metal layer above the at least one second level; forming aconnection to the second metal layer from the fourth metal layer, wherethe connection includes a via through the at least one second level; andforming a fifth metal layer above the fourth metal layer, where the atleast one second level include at least a first oxide layer overlaid bya transistor layer and overlaid by a second oxide layer, where thedistance from the first oxide layer to the second oxide layer is lessthan two microns, where at least one of the plurality of secondtransistors includes a metal gate, and where the fifth metal layerthickness is at least 50% greater than the second metal layer thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be understood and appreciatedmore fully from the following detailed description, taken in conjunctionwith the drawings in which:

FIG. 1 is an exemplary drawing illustration of a 3D integrated circuit;

FIG. 2 is an exemplary drawing illustration of another 3D integratedcircuit;

FIG. 3 is an exemplary drawing illustration of the power distributionnetwork of a 3D integrated circuit;

FIG. 4 is an exemplary drawing illustration of a NAND gate;

FIG. 5 is an exemplary drawing illustration of a thermal contactconcept;

FIG. 6 is an exemplary drawing illustration of various types of thermalcontacts;

FIG. 7 is an exemplary drawing illustration of another type of thermalcontact;

FIG. 8 is an exemplary drawing illustration of the use of heat spreadersin 3D stacked device layers;

FIG. 9 is an exemplary drawing illustration of the use of thermallyconductive shallow trench isolation (STI) in 3D stacked device layers;

FIG. 10 is an exemplary drawing illustration of the use of thermallyconductive pre-metal dielectric regions in 3D stacked device layers;

FIG. 11 is an exemplary drawing illustration of the use of thermallyconductive etch stop layers for the first metal layer of 3D stackeddevice layers;

FIG. 12A-12B are exemplary drawing illustrations of the use andretention of thermally conductive hard mask layers for patterningcontact layers of 3D stacked device layers;

FIG. 13 is an exemplary drawing illustration of a 4 input NAND gate;

FIG. 14 is an exemplary drawing illustration of a 4 input NAND gatewhere substantially all parts of the logic cell can be within desirabletemperature limits;

FIG. 15 is an exemplary drawing illustration of a transmission gate;

FIG. 16 is an exemplary drawing illustration of a transmission gatewhere substantially all parts of the logic cell can be within desirabletemperature limits;

FIG. 17A-17D is an exemplary process flow for constructing recessedchannel transistors with thermal contacts;

FIG. 18 is an exemplary drawing illustration of a pMOS recessed channeltransistor with thermal contacts;

FIG. 19 is an exemplary drawing illustration of a CMOS circuit withrecessed channel transistors and thermal contacts;

FIG. 20 is an exemplary drawing illustration of a technique to removeheat more effectively from silicon-on-insulator (SOI) circuits;

FIG. 21 is an exemplary drawing illustration of an alternative techniqueto remove heat more effectively from silicon-on-insulator (SOI)circuits;

FIG. 22 is an exemplary drawing illustration of a recessed channeltransistor (RCAT);

FIG. 23 is an exemplary drawing illustration of a 3D-IC with thermallyconductive material on the sides;

FIG. 24 is an exemplary procedure for a chip designer to ensure a goodthermal profile for a design;

FIG. 25 is an exemplary drawing illustration of a monolithic 3D-ICstructure with CTE adjusted through layer connections;

FIGS. 26A-26F are exemplary drawing illustrations of a process flow formanufacturing fully depleted Recessed Channel Array Transistors(FD-RCAT);

FIGS. 27A-27B, 27B-1, 27C-27F are exemplary drawing illustrations of theintegration of a shield/heat sink layer in a 3D-IC;

FIGS. 28A-28G, 28G-1 are exemplary drawing illustrations of a processflow for manufacturing fully depleted Recessed Channel Array Transistors(FD-RCAT) with an integrated shield/heat sink layer;

FIGS. 29A-29G, 29G-1 are exemplary drawing illustrations of a processflow for manufacturing fully depleted MOSFET (FD-MOSFET) with anintegrated shield/heat sink layer;

FIGS. 30A-30G are exemplary drawing illustrations of another processflow for manufacturing fully depleted MOSFET (FD-MOSFET) with anintegrated shield/heat sink layer;

FIGS. 31A-31E, 31E-1, 31F, 31G are exemplary drawing illustrations of aprocess flow for manufacturing horizontally oriented JFET or JLT with anintegrated shield/heat sink layer;

FIG. 32 is an exemplary illustration of a partially processed 3D devicewith substrate being processed with topside illumination and includingthermally conductive paths; and

FIG. 33 is an exemplary illustration of some additional embodiments andcombinations of devices, circuits, paths, and connections of a 3Ddevice.

DETAILED DESCRIPTION

An embodiment of the invention is now described with reference to thedrawing figures. Persons of ordinary skill in the art will appreciatethat the description and figures illustrate rather than limit theinvention and that in general the figures are not drawn to scale forclarity of presentation. Such skilled persons will also realize thatmany more embodiments are possible by applying the inventive principlescontained herein and that such embodiments fall within the scope of theinvention which is not to be limited except by the appended claims.

Some drawing figures may describe process flows for building devices.The process flows, which may be a sequence of steps for building adevice, may have many structures, numerals and labels that may be commonbetween two or more adjacent steps. In such cases, some labels, numeralsand structures used for a certain step's figure may have been describedin the previous steps' figures.

FIG. 1 illustrates a 3D integrated circuit. Two crystalline layers, 0104and 0116, which may include semiconductor materials such as, forexample, mono-crystalline silicon, germanium, GaAs, InP, and graphene,are shown. For this illustration, mono-crystalline (single crystal)silicon may be used. Silicon layer 0116 could be thinned down from itsoriginal thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um. Silicon layer 0104 could be thinned down fromits original thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um; however, due to strength considerations, siliconlayer 0104 may also be of thicknesses greater than 100 um, depending on,for example, the strength of bonding to heat removal apparatus 0102.Silicon layer 0104 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 0114, gate dielectric region 0112, source and drain junctionregions (not shown), and shallow trench isolation (STI) regions 0110.Silicon layer 0116 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 0134, gate dielectric region 0132, source and drain junctionregions (not shown), and shallow trench isolation (STI) regions 0130. Athrough-silicon via (TSV) 0118 could be present and may have anassociated surrounding dielectric region 0120. Wiring layers 0108 forsilicon layer 0104 and wiring dielectric regions 0106 may be present andmay form an associated interconnect layer or layers. Wiring layers 0138for silicon layer 0116 and wiring dielectric 0136 may be present and mayform an associated interconnect layer or layers. Through-silicon via(TSV) 0118 may connect to wiring layers 0108 and wiring layers 0138 (notshown). The heat removal apparatus 0102 may include a heat spreaderand/or a heat sink. The heat removal problem for the 3D integratedcircuit shown in FIG. 1 is immediately apparent. The silicon layer 0116is far away from the heat removal apparatus 0102, and it may bedifficult to transfer heat among silicon layer 0116 and heat removalapparatus 0102. Furthermore, wiring dielectric regions 0106 may notconduct heat well, and this increases the thermal resistance amongsilicon layer 0116 and heat removal apparatus 0102. Silicon layer 0104and silicon layer 0116 may be may be substantially absent ofsemiconductor dopants to form an undoped silicon region or layer, ordoped, such as, for example, with elemental or compound species thatform a p+, or p, or p−, or n+, or n, or n− silicon layer or region. Theheat removal apparatus 0102 may include an external surface from whichheat transfer may take place by methods such as air cooling, liquidcooling, or attachment to another heat sink or heat spreader structure.

It should be noted that while in general a heat sink may be an extraheat conducting element bonded with good heat conductivity (or made tobe in contact with) to the back side of the base layer or substrate,such as for example, mono-crystalline bulk silicon or the bulk substrateof an SOI wafer, in many cases the base layer itself could be aneffective heat sink. For example, many silicon wafers are many hundredsof microns thick before extra thinning or back-grinding, and has arelatively high heat capacity in comparison to the transistor layer,which may be less than one micron thick. Accordingly the heat sinkstructure for some devices discussed herein might be the bulk substrateor base layer itself. In addition, when the term ‘bulk body’ is usedherein, it may refer to the base layer or substrate such as amono-crystalline bulk silicon substrate or the bulk substrate of an SOIwafer, such that the bulk body has a greater heat capacity than the 3Dlayer/region structure to which it is thermally connected. Of course,the bulk body may additionally be connected to a heat sink.

FIG. 2 illustrates an exemplary 3D integrated circuit that could beconstructed, for example, using techniques described in U.S. Pat. No.8,273,610, US patent publications 2012/0091587 and 2013/0020707, andpending U.S. patent application Ser. Nos. 13/441,923 and 13/099,010. Thecontents of the foregoing patent and applications are incorporatedherein by reference. Two crystalline layers, 0204 and 0216, which mayinclude semiconductor materials such as, for example, mono-crystallinesilicon, germanium, GaAs, InP, and graphene, are shown. For thisillustration, mono-crystalline (single crystal) silicon may be used.Silicon layer 0216 could be thinned down from its original thickness,and its final thickness could be in the range of about 0.01 um to about50 um, for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um.Silicon layer 0204 could be thinned down from its original thickness,and its final thickness could be in the range of about 0.01 um to about50 um, for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um;however, due to strength considerations, silicon layer 0204 may also beof thicknesses greater than 100 um, depending on, for example, thestrength of bonding to heat removal apparatus 0202. Silicon layer 0204may include transistors such as, for example, MOSFETS, FinFets, BJTs,HEMTs, HBTs, which may include gate electrode region 0214, gatedielectric region 0212, source and drain junction regions (not shown forclarity) and shallow trench isolation (STI) regions 0210. Silicon layer0216 may include transistors such as, for example, MOSFETS, FinFets,BJTs, HEMTs, HBTs, which may include gate electrode region 0234, gatedielectric region 0232, source and drain junction regions (not shown forclarity), and shallow trench isolation (STI) regions 0222. It can beobserved that the STI regions 0222 can go right through to the bottom ofsilicon layer 0216 and provide good electrical isolation. This, however,may cause challenges for heat removal from the STI surroundedtransistors since STI regions 0222 are typically composed of insulatorsthat do not conduct heat well. Therefore, the heat spreadingcapabilities of silicon layer 0216 with STI regions 0222 are low. Athrough-layer via (TLV) 0218 may be present and may include anassociated surrounding dielectric region 0220. Wiring layers 0208 forsilicon layer 0204 and wiring dielectric regions 0206 may be present andmay form an associated interconnect layer or layers. Wiring layers 0238for silicon layer 0216 and wiring dielectric 0236 may be present and mayform an associated interconnect layer or layers. Through-layer via (TLV)0218 may connect to wiring layers 0208 and wiring layers 0238 (notshown). The heat removal apparatus 0202 may include a heat spreaderand/or a heat sink. The heat removal problem for the 3D integratedcircuit shown in FIG. 2 is immediately apparent. The silicon layer 0216may be far away from the heat removal apparatus 0202, and it may bedifficult to transfer heat among silicon layer 0216 and heat removalapparatus 0202. Furthermore, wiring dielectric regions 0206 may notconduct heat well, and this increases the thermal resistance amongsilicon layer 0216 and heat removal apparatus 0202. The heat removalchallenge is further exacerbated by the poor heat spreading propertiesof silicon layer 0216 with STI regions 0222. Silicon layer 0204 andsilicon layer 0216 may be may be substantially absent of semiconductordopants to form an undoped silicon region or layer, or doped, such as,for example, with elemental or compound species that form a p+, or p, orp−, or n+, or n, or n− silicon layer or region. The heat removalapparatus 0202 may include an external surface from which heat transfermay take place by methods such as air cooling, liquid cooling, orattachment to another heat sink or heat spreader structure.

FIG. 3 and FIG. 4 illustrate how the power or ground distributionnetwork of a 3D integrated circuit could assist heat removal. FIG. 3illustrates an exemplary power distribution network or structure of the3D integrated circuit. As shown in FIGS. 1 and 2 , a 3D integratedcircuit, could, for example, be constructed with two silicon layers,first silicon layer 0304 and second silicon layer 0316. The heat removalapparatus 0302 could include, for example, a heat spreader and/or a heatsink. The power distribution network or structure could consist of aglobal power grid 0310 that takes the supply voltage (denoted as V_(DD))from the chip/circuit power pads and transfers V_(DD) to second localpower grid 0308 and first local power grid 0306, which transfers thesupply voltage to logic/memory cells, transistors, and/or gates such assecond transistor 0314 and first transistor 0315. Second layer vias 0318and first layer vias 0312, such as the previously described TSV or TLV,could be used to transfer the supply voltage from the global power grid0310 to second local power grid 0308 and first local power grid 0306.The global power grid 0310 may also be present among first silicon layer0304 and second silicon layer 0316. The 3D integrated circuit could havea similarly designed and laid-out distribution networks, such as forground and other supply voltages, as well. The power grid may bedesigned and constructed such that each layer or strata of transistorsand devices may be supplied with a different value Vdd. For example,first silicon layer 0304 may be supplied by its power grid to have a Vddvalue of 1.0 volts and second silicon layer 0316 a Vdd value of 0.8volts. Furthermore, the global power grid 0310 wires may be constructedwith substantially higher current conduction, for example 30% higher,50% higher, 2× higher, than local power grids, for example, such asfirst local power grid 0306 wires and second local power grid 0308wires. The thickness, linewidth, and material composition for the globalpower grid 0310 wires may provide for the higher current conduction, forexample, the thickness of the global power grid 0310 wires may be twicethat of the local power grid wires and/or the linewidth of the globalpower grid 0310 wires may be 2× that of the local power grid wires.Moreover, the global power grid 0310 may be optimally located in the topstrata or layer of transistors and devices. Noise on the power grids,such as the Vss and/or Vdd supply grids, may be mitigated byattaching/connecting decoupling capacitors onto the power conductinglines of the grid(s), such as global power grid 0310, first local powergrid 0306 wires and second local power grid 0308 wires. The decouplingcaps may include, for example, trench capacitors such as described byPei, C., et al., “A novel, low-cost deep trench decoupling capacitor forhigh-performance, low-power bulk CMOS applications,” ICSICT (9^(th)International Conference on Solid-State and Integrated-CircuitTechnology) 2008, October 2008, pp. 1146-1149, of IBM. The decouplingcapacitors may include, for example, planar capacitors, such as poly tosubstrate or poly to poly, or MiM capacitors (Metal-Insulator-Metal).

Typically, many contacts may be made among the supply and grounddistribution networks and first silicon layer 0304. Due to this, therecould exist a low thermal resistance among the power/ground distributionnetwork and the heat removal apparatus 0302. Since power/grounddistribution networks may be typically constructed of conductive metalsand could have low effective electrical resistance, the power/grounddistribution networks could have a low thermal resistance as well. Eachlogic/memory cell or gate on the 3D integrated circuit (such as, forexample, second transistor 0314) is typically connected to V_(DD) andground, and therefore could have contacts to the power and grounddistribution network. The contacts could help transfer heat efficiently(for example, with low thermal resistance) from each logic/memory cellor gate on the 3D integrated circuit (such as, for example, secondtransistor 0314) to the heat removal apparatus 0302 through thepower/ground distribution network and the silicon layer 0304. Siliconlayer 0304 and silicon layer 0316 may be may be substantially absent ofsemiconductor dopants to form an undoped silicon region or layer, ordoped, such as, for example, with elemental or compound species thatform a p+, or p, or p−, or n+, or n, or n− silicon layer or region. Theheat removal apparatus 0302 may include an external surface from whichheat transfer may take place by methods such as air cooling, liquidcooling, or attachment to another heat sink or heat spreader structure.

FIG. 4 illustrates an exemplary NAND logic cell or NAND gate 0420 andhow substantially all portions of this logic cell or gate could bedesigned and laid-out with low thermal resistance to the V_(DD) orground (GND) contacts. The NAND gate 0420 could include two pMOStransistors 0402 and two nMOS transistors 0404. The layout of the NANDgate 0420 is indicated in exemplary layout 0422. Various regions of thelayout may include metal regions 0406, poly regions 0408, n type siliconregions 0410, p type silicon regions 0412, contact regions 0414, andoxide regions 0424. pMOS transistors 0416 and nMOS transistors 0418 maybe present in the layout. It can be observed that substantially allparts of the exemplary NAND gate 0420 could have low thermal resistanceto V_(DD) or GND contacts since they may be physically very close tothem, within a few design rule lambdas, wherein lamda is the basicminimum layout rule distance for a given set of circuit layout designrules. Thus, substantially all transistors in the NAND gate 0420 can bemaintained at desirable temperatures, such as, for example, less than 25or 50 or 70 degrees Centigrade, if the V_(DD) or ground contacts aremaintained at desirable temperatures.

While the previous paragraph described how an existing powerdistribution network or structure can transfer heat efficiently fromlogic/memory cells or gates in 3D-ICs to their heat sink, manytechniques to enhance this heat transfer capability will be describedherein. Many embodiments of the invention can provide several benefits,including lower thermal resistance and the ability to cool higher power3D-ICs. As well, thermal contacts may provide mechanical stability andstructural strength to low-k Back End Of Line (BEOL) structures, whichmay need to accommodate shear forces, such as from CMP and/or cleavingprocesses. The heat transfer capability enhancement techniques may beuseful and applied to different methodologies and implementations of3D-ICs, including monolithic 3D-ICs and TSV-based 3D-ICs. The heatremoval apparatus employed, which may include heat sinks and heatspreaders, may include an external surface from which heat transfer maytake place by methods such as air cooling, liquid cooling, or attachmentto another heat sink or heat spreader structure.

FIG. 5 illustrates an embodiment of the invention, wherein thermalcontacts in a 3D-IC is described. The 3D-IC and associated power andground distribution network may be formed as described in FIGS. 1, 2, 3,and 4 herein. For example, two crystalline layers, 0504 and 0516, whichmay include semiconductor materials such as, for example,mono-crystalline silicon, germanium, GaAs, InP, and graphene, may havetransistors. For this illustration, mono-crystalline (single crystal)silicon may be used. Silicon layer 0516 could be thinned down from itsoriginal thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um. Silicon layer 0504 could be thinned down fromits original thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um; however, due to strength considerations, siliconlayer 0504 may also be of thicknesses greater than 100 um, depending on,for example, the strength of bonding to heat removal apparatus 0202.Silicon layer 0504 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include STI regions 0510,gate dielectric regions 0512, gate electrode regions 0514 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). Silicon layer 0516 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include STI regions 0530, gate dielectric regions 0532,gate electrode regions 0534 and several other regions that may benecessary for transistors such as source and drain junction regions (notshown for clarity). Heat removal apparatus 0502 may include, forexample, heat spreaders and/or heat sinks. In the example shown in FIG.5 , silicon layer 0504 is closer to the heat removal apparatus 0502 thanother silicon layers such as silicon layer 0516. Wiring layers 0542 forsilicon layer 0504 and wiring dielectric 0546 may be present and mayform an associated interconnect layer or layers. Wiring layers 0522 forsilicon layer 0516 and wiring dielectric 0506 may be present and mayform an associated interconnect layer or layers. Through-layer vias(TLVs) 0518 for power delivery and interconnect and their associateddielectric regions 0520 are shown. Dielectric regions 0520 may includeSTI regions, such as STI regions 0530. A thermal contact 0524 mayconnect the local power distribution network or structure to the siliconlayer 0504. The local power distribution network or structure mayinclude wiring layers 0542 used for transistors in the silicon layer0504. Thermal junction region 0526 can be, for example, a doped orundoped region of silicon, and further details of thermal junctionregion 0526 will be given in FIG. 6 . The thermal contact 0524 can besuitably placed close to the corresponding through-layer via 0518; thishelps transfer heat efficiently as a thermal conduction path from thethrough-layer via 0518 to thermal junction region 0526 and silicon layer0504 and ultimately to the heat removal apparatus 0502. For example, thethermal contact 0524 could be located within approximately 2 um distanceof the through-layer via 0518 in the X-Y plane (the through-layer via0518 vertical length direction is considered the Z plane in FIG. 5 ).While the thermal contact 0524 is described above as being between thepower distribution network or structure and the silicon layer closest tothe heat removal apparatus, it could also be between the grounddistribution network and the silicon layer closest to the heat sink.Furthermore, more than one thermal contact 0524 can be placed close tothe through-layer via 0518. The thermal contacts can improve heattransfer from transistors located in higher layers of silicon such assilicon layer 0516 to the heat removal apparatus 0502. Whilemono-crystalline silicon has been mentioned as the transistor materialin this document, other options are possible including, for example,poly-crystalline silicon, mono-crystalline germanium, mono-crystallineIII-V semiconductors, graphene, and various other semiconductormaterials with which devices, such as transistors, may be constructedwithin. Moreover, thermal contacts and vias may not be stacked in avertical line through multiple stacks, layers, strata of circuits.Thermal contacts and vias may include materials such as sp2 carbon asconducting and sp3 carbon as non-conducting of electrical current.Thermal contacts and vias may include materials such as carbonnano-tubes. Thermal contacts and vias may include materials such as, forexample, copper, aluminum, tungsten, titanium, tantalum, cobalt metalsand/or silicides of the metals. Silicon layer 0504 and silicon layer0516 may be may be substantially absent of semiconductor dopants to forman undoped silicon region or layer, or doped, such as, for example, withelemental or compound species that form a p+, or p, or p−, or n+, or n,or n− silicon layer or region. The heat removal apparatus 0502 mayinclude an external surface from which heat transfer may take place bymethods such as air cooling, liquid cooling, or attachment to anotherheat sink or heat spreader structure.

FIG. 6 describes an embodiment of the invention, wherein variousimplementations of thermal junctions and associated thermal contacts areillustrated. P-wells in CMOS integrated circuits may be typically biasedto ground and N-wells may be typically biased to the supply voltageV_(DD). A thermal contact 0604 between the power (V_(DD)) distributionnetwork and a P-well 0602 can be implemented as shown in N+ in P-wellthermal junction and contact example 0608, where an n+ doped regionthermal junction 0606 may be formed in the P-well region at the base ofthe thermal contact 0604. The n+ doped region thermal junction 0606ensures a reverse biased p-n junction can be formed in N+ in P-wellthermal junction and contact example 0608 and makes the thermal contactviable (for example, not highly conductive) from an electricalperspective. The thermal contact 0604 could be formed of a conductivematerial such as copper, aluminum or some other material with a thermalconductivity of at least 100 W/m-K. A thermal contact 0614 between theground (GND) distribution network and a P-well 0612 can be implementedas shown in P+ in P-well thermal junction and contact example 0618,where a p+ doped region thermal junction 0616 may be formed in theP-well region at the base of the thermal contact 0614. The p+ dopedregion thermal junction 0616 makes the thermal contact viable (forexample, not highly conductive) from an electrical perspective. The p+doped region thermal junction 0616 and the P-well 0612 may typically bebiased at ground potential. The thermal contact 0614 could be formed ofa conductive material such as copper, aluminum or some other materialwith a thermal conductivity of at least 100 W/m-K. A thermal contact0624 between the power (V_(DD)) distribution network and an N-well 0622can be implemented as shown in N+ in N-well thermal junction and contactexample 0628, wherein an n+ doped region thermal junction 0626 may beformed in the N-well region at the base of the thermal contact 0624. Then+ doped region thermal junction 0626 makes the thermal contact viable(for example, not highly conductive) from an electrical perspective. Then+ doped region thermal junction 0626 and the N-well 0622 may typicallybe biased at V_(DD) potential. The thermal contact 0624 could be formedof a conductive material such as copper, aluminum or some other materialwith a thermal conductivity of at least 100 W/m-K. A thermal contact0634 between the ground (GND) distribution network and an N-well 0632can be implemented as shown in P+ in N-well thermal junction and contactexample 0638, where a p+ doped region thermal junction 0636 may beformed in the N-well region at the base of the thermal contact 0634. Thep+ doped region thermal junction 0636 makes the thermal contact viable(for example, not highly conductive) from an electrical perspective dueto the reverse biased p-n junction formed in P+ in N-well thermaljunction and contact example 0638. The thermal contact 0634 could beformed of a conductive material such as copper, aluminum or some othermaterial with a thermal conductivity of at least 100 W/m-K. Note thatthe thermal contacts are designed to conduct negligible electricity, andthe current flowing through them is several orders of magnitude lowerthan the current flowing through a transistor when it is switching.Therefore, the thermal contacts can be considered to be designed toconduct heat and conduct negligible (or no) electricity.

FIG. 7 describes an embodiment of the invention, wherein an additionaltype of thermal contact structure is illustrated. The embodiment shownin FIG. 7 could also function as a decoupling capacitor to mitigatepower supply noise. It could consist of a thermal contact 0704, anelectrode 0710, a dielectric 0706 and P-well 0702. The dielectric 0706may be electrically insulating, and could be optimized to have highthermal conductivity. Dielectric 0706 could be formed of materials, suchas, for example, hafnium oxide, silicon dioxide, other high kdielectrics, carbon, carbon based material, or various other dielectricmaterials with electrical conductivity below 1 nano-amp per squaremicron.

A thermal connection may be defined as the combination of a thermalcontact and a thermal junction. The thermal connections illustrated inFIG. 6 , FIG. 7 and other figures in this document are designed into achip to remove heat, and are designed to not conduct electricity.Essentially, a semiconductor device including power distribution wiresis described wherein some of said wires have a thermal connectiondesigned to conduct heat to the semiconductor layer and the wires do notsubstantially conduct electricity through the thermal connection to thesemiconductor layer.

Thermal contacts similar to those illustrated in FIG. 6 and FIG. 7 canbe used in the white spaces of a design, for example, locations of adesign where logic gates or other useful functionality may not bepresent. The thermal contacts may connect white-space silicon regions topower and/or ground distribution networks. Thermal resistance to theheat removal apparatus can be reduced with this approach. Connectionsamong silicon regions and power/ground distribution networks can be usedfor various device layers in the 3D stack, and may not be restricted tothe device layer closest to the heat removal apparatus. A Schottkycontact or diode may also be utilized for a thermal contact and thermaljunction. Moreover, thermal contacts and vias may not have to be stackedin a vertical line through multiple stacks, layers, strata of circuits.

FIG. 8 illustrates an embodiment of the invention, which can provideenhanced heat removal from 3D-ICs by integrating heat spreader regionsin stacked device layers. The 3D-IC and associated power and grounddistribution network may be formed as described in FIGS. 1, 2, 3, 4, and5 herein. For example, two crystalline layers, 0804 and 0816, which mayinclude semiconductor materials such as, for example, mono-crystallinesilicon, germanium, GaAs, InP, and graphene, are shown. For thisillustration, mono-crystalline (single crystal) silicon may be used.Silicon layer 0816 could be thinned from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Siliconlayer 0804 could be thinned down from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um; however,due to strength considerations, silicon layer 0804 may also be ofthicknesses greater than 100 um, depending on, for example, the strengthof bonding to heat removal apparatus 0802. Silicon layer 0804 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 0814, gate dielectricregion 0812, shallow trench isolation (STI) regions 0810 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). Silicon layer 0816 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 0834, gate dielectricregion 0832, shallow trench isolation (STI) regions 0822 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). A through-layer via(TLV) 0818 may be present and may include an associated surroundingdielectric region 0820. Wiring layers 0808 for silicon layer 0804 andwiring dielectric 0806 may be present and may form an associatedinterconnect layer or layers. Wiring layers 0838 for silicon layer 0816and wiring dielectric 0836 may be present and may form an associatedinterconnect layer or layers. Through-layer via (TLV) 0818 may connectto wiring layers 0808 and wiring layers 0838 (not shown). The heatremoval apparatus 0802 may include, for example, a heat spreader and/ora heat sink. It can be observed that the STI regions 0822 can go rightthrough to the bottom of silicon layer 0816 and provide good electricalisolation. This, however, may cause challenges for heat removal from theSTI surrounded transistors since STI regions 0822 are typically composedof insulators that do not conduct heat well. The buried oxide layer 0824typically does not conduct heat well. To tackle heat removal issues withthe structure shown in FIG. 8 , a heat spreader 0826 may be integratedinto the 3D stack. The heat spreader 0826 material may include, forexample, copper, aluminum, graphene, diamond, carbon or any othermaterial with a high thermal conductivity (defined as greater than 10W/m-K). While the heat spreader concept for 3D-ICs is described with anarchitecture similar to FIG. 2 , similar heat spreader concepts could beused for architectures similar to FIG. 1 , and also for other 3D ICarchitectures. Silicon layer 0804 and silicon layer 0816 may be may besubstantially absent of semiconductor dopants to form an undoped siliconregion or layer, or doped, such as, for example, with elemental orcompound species that form a p+, or p, or p−, or n+, or n, or n− siliconlayer or region. The heat removal apparatus 0802 may include an externalsurface from which heat transfer may take place by methods such as aircooling, liquid cooling, or attachment to another heat sink or heatspreader structure.

FIG. 9 illustrates an embodiment of the invention, which can provideenhanced heat removal from 3D-ICs by using thermally conductive shallowtrench isolation (STI) regions in stacked device layers. The 3D-IC andassociated power and ground distribution network may be formed asdescribed in FIGS. 1, 2, 3, 4, 5 and 8 herein. For example, twocrystalline layers, 0904 and 0916, which may include semiconductormaterials such as, for example, mono-crystalline silicon, germanium,GaAs, InP, and graphene, are shown. For this illustration,mono-crystalline (single crystal) silicon may be used. Silicon layer0916 could be thinned from its original thickness, and its finalthickness could be in the range of about 0.01 um to about 50 um, forexample, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Siliconlayer 0904 could be thinned down from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um; however,due to strength considerations, silicon layer 0904 may also be ofthicknesses greater than 100 um, depending on, for example, the strengthof bonding to heat removal apparatus 0802. Silicon layer 0904 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 0914, gate dielectricregion 0912, shallow trench isolation (STI) regions 0910 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). Silicon layer 0916 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 0934, gate dielectricregion 0932, shallow trench isolation (STI) regions 0922 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). A through-layer via(TLV) 0918 may be present and may include an associated surroundingdielectric region 0920. Dielectric region 0920 may include a shallowtrench isolation region. Wiring layers 0908 for silicon layer 0904 andwiring dielectric 0906 may be present and may form an associatedinterconnect layer or layers. Wiring layers 0938 for silicon layer 0916and wiring dielectric 0936 may be present and may form an associatedinterconnect layer or layers. Through-layer via (TLV) 0918 may connectto wiring layers 0908 and wiring layers 0938 (not shown). The heatremoval apparatus 0902 may include a heat spreader and/or a heat sink.It can be observed that the STI regions 0922 can go right through to thebottom of silicon layer 0916 and provide good electrical isolation.This, however, may cause challenges for heat removal from the STIsurrounded transistors since STI regions 0922 are typically composed ofinsulators such as silicon dioxide that do not conduct heat well. Totackle possible heat removal issues with the structure shown in FIG. 9 ,the STI regions 0922 in stacked silicon layers such as silicon layer0916 could be formed substantially of thermally conductive dielectricsincluding, for example, diamond, carbon, or other dielectrics that havea thermal conductivity higher than silicon dioxide and/or have a thermalconductivity higher than 0.6 W/m-K. This structure can provide enhancedheat spreading in stacked device layers. Thermally conductive STIdielectric regions could be used in the vicinity of the transistors instacked 3D device layers and may also be utilized as the dielectric thatsurrounds TLV 0918, such as dielectric region 0920. While the thermallyconductive shallow trench isolation (STI) regions concept for 3D-ICs isdescribed with an architecture similar to FIG. 2 , similar thermallyconductive shallow trench isolation (STI) regions concepts could be usedfor architectures similar to FIG. 1 , and also for other 3D ICarchitectures and 2D IC as well. Silicon layer 0904 and silicon layer0916 may be may be substantially absent of semiconductor dopants to forman undoped silicon region or layer, or doped, such as, for example, withelemental or compound species that form a p+, or p, or p−, or n+, or n,or n− silicon layer or region. The heat removal apparatus 0902 mayinclude an external surface from which heat transfer may take place bymethods such as air cooling, liquid cooling, or attachment to anotherheat sink or heat spreader structure.

FIG. 10 illustrates an embodiment of the invention, which can provideenhanced heat removal from 3D-ICs using thermally conductive pre-metaldielectric regions in stacked device layers. The 3D-IC and associatedpower and ground distribution network may be formed as described inFIGS. 1, 2, 3, 4, 5, 8 and 9 herein. For example, two crystallinelayers, 1004 and 1016, which may include semiconductor materials suchas, for example, mono-crystalline silicon, germanium, GaAs, InP, andgraphene, are shown. For this illustration, mono-crystalline (singlecrystal) silicon may be used. Silicon layer 1016 could be thinned fromits original thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um. Silicon layer 1004 could be thinned down fromits original thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um; however, due to strength considerations, siliconlayer 1004 may also be of thicknesses greater than 100 um, depending on,for example, the strength of bonding to heat removal apparatus 1002.Silicon layer 1004 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 1014, gate dielectric region 1012, shallow trench isolation (STI)regions 1010 and several other regions that may be necessary fortransistors such as source and drain junction regions (not shown forclarity). Silicon layer 1016 may include transistors such as, forexample, MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gateelectrode region 1034, gate dielectric region 1032, shallow trenchisolation (STI) regions 1022 and several other regions that may benecessary for transistors such as source and drain junction regions (notshown for clarity). A through-layer via (TLV) 1018 may be present andmay include an associated surrounding dielectric region 1020, which mayinclude an STI region. Wiring layers 1008 for silicon layer 1004 andwiring dielectric 1006 may be present and may form an associatedinterconnect layer or layers. Wiring layers 1038 for silicon layer 1016and wiring dielectric 1036 may be present and may form an associatedinterconnect layer or layers. Through-layer via (TLV) 1018 may connectto wiring layers 1008 (not shown). The heat removal apparatus 1002 mayinclude, for example, a heat spreader and/or a heat sink. It can beobserved that the STI regions 1022 can go right through to the bottom ofsilicon layer 1016 and provide good electrical isolation. This, however,can cause challenges for heat removal from the STI surroundedtransistors since STI regions 1022 are typically filled with insulatorssuch as silicon dioxide that do not conduct heat well. To tackle thisissue, the inter-layer dielectrics (ILD) 1024 for contact region 1026could be constructed substantially with a thermally conductive material,such as, for example, insulating carbon, diamond, diamond like carbon(DLC), and various other materials that provide better thermalconductivity than silicon dioxide or have a thermal conductivity higherthan 0.6 W/m-K. Thermally conductive pre-metal dielectric regions couldbe used around some of the transistors in stacked 3D device layers.While the thermally conductive pre-metal dielectric regions concept for3D-ICs is described with an architecture similar to FIG. 2 , similarthermally conductive pre-metal dielectric region concepts could be usedfor architectures similar to FIG. 1 , and also for other 3D ICarchitectures and 2D IC as well. Silicon layer 1004 and silicon layer1016 may be may be substantially absent of semiconductor dopants to forman undoped silicon region or layer, or doped, such as, for example, withelemental or compound species that form a p+, or p, or p−, or n+, or n,or n− silicon layer or region. The heat removal apparatus 1002 mayinclude an external surface from which heat transfer may take place bymethods such as air cooling, liquid cooling, or attachment to anotherheat sink or heat spreader structure.

FIG. 11 describes an embodiment of the invention, which can provideenhanced heat removal from 3D-ICs using thermally conductive etch stoplayers or regions for the first metal level of stacked device layers.The 3D-IC and associated power and ground distribution network may beformed as described in FIGS. 1, 2, 3, 4, 5, 8, 9 and 10 herein. Forexample, two crystalline layers, 1104 and 1116, which may includesemiconductor materials such as, for example, mono-crystalline silicon,germanium, GaAs, InP, and graphene, are shown. For this illustration,mono-crystalline (single crystal) silicon may be used. Silicon layer1116 could be thinned from its original thickness, and its finalthickness could be in the range of about 0.01 um to about 50 um, forexample, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Siliconlayer 1104 could be thinned down from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um; however,due to strength considerations, silicon layer 1104 may also be ofthicknesses greater than 100 um, depending on, for example, the strengthof bonding to heat removal apparatus 1102. Silicon layer 1104 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 1114, gate dielectricregion 1112, shallow trench isolation (STI) regions 1110 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). Silicon layer 1116 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 1134, gate dielectricregion 1132, shallow trench isolation (STI) regions 1122 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). A through-layer via(TLV) 1118 may be present and may include an associated surroundingdielectric region 1120. Wiring layers 1108 for silicon layer 1104 andwiring dielectric 1106 may be present and may form an associatedinterconnect layer or layers. Wiring layers for silicon layer 1116 mayinclude first metal layer 1128 and other metal layers 1138 and wiringdielectric 1136 and may form an associated interconnect layer or layers.The heat removal apparatus 1102 may include, for example, a heatspreader and/or a heat sink. It can be observed that the STI regions1122 can go right through to the bottom of silicon layer 1116 andprovide good electrical isolation. This, however, can cause challengesfor heat removal from the STI surrounded transistors since STI regions1122 are typically filled with insulators such as silicon dioxide thatdo not conduct heat well. To tackle this issue, etch stop layer 1124 aspart of the process of constructing the first metal layer 1128 ofsilicon layer 1116 can be substantially constructed out of a thermallyconductive but electrically isolative material. Examples of suchthermally conductive materials could include insulating carbon, diamond,diamond like carbon (DLC), and various other materials that providebetter thermal conductivity than silicon dioxide and silicon nitride,and/or have thermal conductivity higher than 0.6 W/m-K. Thermallyconductive etch-stop layer dielectric regions could be used for thefirst metal layer above transistors in stacked 3D device layers. Whilethe thermally conductive etch stop layers or regions concept for 3D-ICsis described with an architecture similar to FIG. 2 , similar thermallyconductive etch stop layers or regions concepts could be used forarchitectures similar to FIG. 1 , and also for other 3D IC architecturesand 2D IC as well. Silicon layer 1104 and silicon layer 1116 may be maybe substantially absent of semiconductor dopants to form an undopedsilicon region or layer, or doped, such as, for example, with elementalor compound species that form a p+, or p, or p−, or n+, or n, or n−silicon layer or region. The heat removal apparatus 1102 may include anexternal surface from which heat transfer may take place by methods suchas air cooling, liquid cooling, or attachment to another heat sink orheat spreader structure.

FIG. 12A-B describes an embodiment of the invention, which can provideenhanced heat removal from 3D-ICs using thermally conductive layers orregions as part of pre-metal dielectrics for stacked device layers. The3D-IC and associated power and ground distribution network may be formedas described in FIGS. 1, 2, 3, 4, 5, 8, 9, 10 and 11 herein. Forexample, two crystalline layers, 1204 and 1216, are shown and may havetransistors. For this illustration, mono-crystalline (single crystal)silicon may be used. Silicon layer 1216 could be thinned from itsoriginal thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um. Silicon layer 1204 could be thinned down fromits original thickness, and its final thickness could be in the range ofabout 0.01 um to about 50 um, for example, 10 nm, 100 nm, 200 nm, 0.4um, 1 um, 2 um or 5 um; however, due to strength considerations, siliconlayer 1204 may also be of thicknesses greater than 100 um, depending on,for example, the strength of bonding to heat removal apparatus 1202.Silicon layer 1204 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 1214, gate dielectric region 1212, shallow trench isolation (STI)regions 1210 and several other regions that may be necessary fortransistors such as source and drain junction regions (not shown forclarity). Silicon layer 1216 may include transistors such as, forexample, MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gateelectrode region 1234, gate dielectric region 1232, shallow trenchisolation (STI) regions 1222 and several other regions that may benecessary for transistors such as source and drain junction regions (notshown for clarity). A through-layer via (TLV) 1218 may be present andmay include an associated surrounding dielectric region 1220. Wiringlayers 1208 for silicon layer 1204 and wiring dielectric 1206 may bepresent and may form an associated interconnect layer or layers.Through-layer via (TLV) 1218 may connect to wiring layers 1208 andfuture wiring layers such as those for interconnection of silicon layer1216 transistors (not shown). The heat removal apparatus 1202 mayinclude a heat spreader and/or a heat sink. It can be observed that theSTI regions 1222 can go right through to the bottom of silicon layer1216 and provide good electrical isolation. This, however, can causechallenges for heat removal from the STI surrounded transistors sinceSTI regions 1222 are typically filled with insulators such as silicondioxide that do not conduct heat well. To tackle this issue, a techniqueis described in FIG. 12A-B. FIG. 12A illustrates the formation ofopenings for making contacts to the transistors of silicon layer 1216. Ahard mask layer 1224 or region is typically used during the lithographystep for contact formation and hard mask layer 1224 or region may beutilized to define contact opening regions 1226 of the pre-metaldielectric 1230 that is etched away. FIG. 12B illustrates the contact1228 formed after metal is filled into the contact opening regions 1226shown in FIG. 12A, and after a chemical mechanical polish (CMP) process.The hard mask layer 1224 or region used for the process shown in FIG.12A-B may include a thermally conductive but electrically isolativematerial. Examples of such thermally conductive materials could includeinsulating carbon, diamond, diamond like carbon (DLC), and various othermaterials that provide better thermal conductivity than silicon dioxideand silicon nitride, and/or have thermal conductivity higher than 0.6W/m-K and can be left behind after the process step shown in FIG. 12B(hence, electrically non-conductive). Further steps for forming the3D-IC (such as forming additional metal layers) may be performed (notshown). While the thermally conductive materials for hard mask conceptfor 3D-ICs is described with an architecture similar to FIG. 2 , similarthermally conductive materials for hard mask concepts could be used forarchitectures similar to FIG. 1 , and also for other 3D IC architecturesand 2D IC as well. Silicon layer 1204 and silicon layer 1216 may be maybe substantially absent of semiconductor dopants to form an undopedsilicon region or layer, or doped, such as, for example, with elementalor compound species that form a p+, or p, or p−, or n+, or n, or n−silicon layer or region. The heat removal apparatus 1202 may include anexternal surface from which heat transfer may take place by methods suchas air cooling, liquid cooling, or attachment to another heat sink orheat spreader structure.

FIG. 13 illustrates the layout of an exemplary 4-input NAND gate 1300,where the output OUT is a function of inputs A, B, C and D. 4-input NANDgate 1300 may include metal 1 regions 1306, gate regions 1308, N-typesilicon regions 1310, P-type silicon regions 1312, contact regions 1314,and oxide isolation regions 1316. If the 4-input NAND gate 1300 is usedin 3D IC stacked device layers, some regions of the NAND gate (such as,for example, sub-region 1318 of N-type silicon regions 1310) are faraway from V_(DD) and GND contacts of 4-input NAND gate 1300. Theregions, such as sub-region 1318, could have a high thermal resistanceto V_(DD) and GND contacts, and could heat up to undesired temperatures.This is because the regions of the NAND gate far away from V_(DD) andGND contacts cannot effectively use the low-thermal resistance powerdelivery network to transfer heat to the heat removal apparatus.

FIG. 14 illustrates an embodiment of the invention wherein the layout ofexemplary 3D stackable 4-input NAND gate 1400 can be modified so thatsubstantially all parts of the gate are at desirable temperatures duringchip operation. Desirable temperatures during chip operation may dependon the type of transistors, circuits, and product application & use, andmay be, for example, sub-150° C., sub-100° C., sub-75° C., sub-50° C. orsub-25° C. Inputs to the 3D stackable 4-input NAND gate 1400 are denotedas A, B, C and D, and the output is denoted as OUT. The 4-input NANDgate 1400 may include metal 1 regions 1406, gate regions 1408, N-typesilicon regions 1410, P-type silicon regions 1412, contact regions 1414,and oxide isolation regions 1416. As discussed above, sub-region 1418could have a high thermal resistance to V_(DD) and GND contacts andcould heat up to undesired temperatures. Thermal contact 1420 (whoseimplementation can be similar to those described in FIG. 6 and FIG. 7 )may be added to the layout, for example as shown in FIG. 13 , to keepthe temperature of sub-region 1418 within desirable limits by reducingthe thermal resistance from sub-region 1418 to the GND distributionnetwork. Several other implementations of adding and placement ofthermal contacts that would be appreciated by persons of ordinary skillin the art can be used to make the exemplary layout shown in FIG. 14more desirable from a thermal perspective.

FIG. 15 illustrates the layout of an exemplary transmission gate 1500with control inputs A and A′ (A′ typically the inversion of A).Transmission gate 1500 may include metal 1 regions 1506, gate regions1508, N-type silicon regions 1510, P-type silicon regions 1512, contactregions 1514, and oxide isolation regions 1516. If transmission gate1500 is used in 3D IC stacked device layers, some regions of thetransmission gate could heat up to undesired temperatures since thereare no V_(DD) and GND contacts. There could be a high thermal resistanceto V_(DD) and GND distribution networks. Thus, the transmission gatecannot effectively use the low-thermal resistance power delivery networkto transfer heat to the heat removal apparatus. Transmission gate is oneexample of transistor function that might not include any connection tothe power grid and accordingly there may not be a good thermal path toremove the built-up heat. Sometimes in a 3D structure the transistorisolation may be achieved by etching around the transistor or transistorfunction substantially all of the silicon and filling it with anelectrically isolative material, such as, for example, silicon oxides,which might have a poor thermal conduction. As such, the transistor ortransistor function may not have an effective thermal path to removeheat build-up. There are other functions, such as, for example, SRAMselect transistors and Look-Up-Table select transistors, which may usetransistors with no power grid (Vdd, Vss) connections (may only havesignal connections) which may be subject to the same heat removalproblem.

FIG. 16 illustrates an embodiment of the invention wherein the layout ofexemplary 3D stackable transmission gate 1600 can be modified so thatsubstantially all parts of the gate, channel, and transistor body are atdesirable temperatures during chip operation. Desirable temperaturesduring chip operation may depend on the type of transistors, circuits,and product application & use, and may be, for example, sub-150° C.,sub-100° C., sub-75° C., sub-50° C. or sub-25° C. Control signals to the3D stackable transmission gate 1600 are denoted as A and A′ (A′typically the inversion of A). 3D stackable transmission gate 1600 mayinclude metal 1 regions 1606, gate regions 1608, N-type silicon regions1610, P-type silicon regions 1612, contact regions 1614, and oxideisolation regions 1616. Thermal contacts, such as, for example thermalcontact 1620 and second thermal contact 1622 (whose implementation canbe similar to those described in FIG. 6 and FIG. 7 ) may be added to thelayout shown in FIG. 15 to keep the temperature of 3D stackabletransmission gate 1600 within desirable limits (by reducing the thermalresistance to the V_(DD) and GND distribution networks). The thermalpaths may use a reverse bias diode in at least one portion so that thethermal path may conduct heat but does not conduct current or anelectric signal, and accordingly does not interfere with the properoperation of the transistor function. Several other implementations ofadding and placement of thermal contacts that would be appreciated bypersons of ordinary skill in the art can be used to make the exemplarylayout, such as shown in FIG. 16 , more desirable from a thermalperspective.

The techniques illustrated with FIG. 14 and FIG. 16 are not restrictedto cells such as transmission gates and NAND gates, and can be appliedto a number of cells such as, for example, SRAMs, CAMs, multiplexers andmany others. Furthermore, the techniques illustrated with at least FIG.14 and FIG. 16 can be applied and adapted to various techniques ofconstructing 3D integrated circuits and chips, including those describedin U.S. Pat. No. 8,273,610, US patent publications 2012/0091587 and2013/0020707, and pending U.S. patent application Ser. Nos. 13/441,923and 13/099,010. The contents of the foregoing applications areincorporated herein by reference. Furthermore, techniques illustratedwith FIG. 14 and FIG. 16 (and other similar techniques) need not beapplied to substantially all such gates on the chip, but could beapplied to a portion of gates of that type, such as, for example, gateswith higher activity factor, lower threshold voltage or higher drivecurrent. Moreover, thermal contacts and vias may not have to be stackedin a vertical line through multiple stacks, layers, strata of circuits.

When a chip is typically designed a cell library consisting of variouslogic cells such as NAND gates, NOR gates and other gates is created,and the chip design flow proceeds using this cell library. It will beclear to one skilled in the art that a cell library may be createdwherein each cell's layout can be optimized from a thermal perspectiveand based on heat removal criteria such as maximum allowable transistorchannel temperature (for example, where each cell's layout can beoptimized such that substantially all portions of the cell have lowthermal resistance to the V_(DD) and GND contacts, and therefore, to thepower bus and the ground bus).

FIG. 24 illustrates a procedure for a chip designer to ensure a goodthermal profile for his or her design. After a first pass or a portionof the first pass of the desired chip layout process is complete, athermal analysis may be conducted to determine temperature profiles foractive or passive elements, such as gates, on the 3D chip. The thermalanalysis may be started (2400). The temperature of any stacked gate, orregion of gates, may be calculated, for example, by simulation such as amulti-physics solver, and compared to a desired specification value(2410). If the gate, or region of gates, temperature is higher than thespecification, which may, for example, be in the range of 65° C.-150°C., modifications (2420) may be made to the layout or design, such as,for example, power grids for stacked layers may be made denser or wider,additional contacts to the gate may be added, more through-silicon (TLVand/or TSV) connections may be made for connecting the power grid instacked layers to the layer closest to the heat sink, or any othermethod to reduce stacked layer temperature that may be described hereinor in referenced documents, which may be used alone or in combination.The output (2430) may give the designer the temperature of the modifiedstacked gate (‘Yes’ tree), or region of gates, or an unmodified one(‘No’ tree), and may include the original un-modified gate temperaturethat was above the desired specification. The thermal analysis may end(2440) or may be iterated. Alternatively, the power grid may be designed(based on heat removal criteria) simultaneously with the logic gates andlayout of the design, or for various regions of any layer of the 3Dintegrated circuit stack. The density of TLVs may be greater than 10⁴per cm², and may be 10×, 100×, 1000×, denser than TSVs.

Recessed channel transistors form a transistor family that can bestacked in 3D. FIG. 22 illustrates an exemplary Recessed ChannelTransistor 2200 which may be constructed in a 3D stacked layer usingprocedures outlined in U.S. Pat. No. 8,273,610, US patent publications2012/0091587 and 2013/0020707, and pending U.S. patent application Ser.Nos. 13/441,923 and 13/099,010. The contents of the foregoing patent andapplications are incorporated herein by reference. Recessed ChannelTransistor 2200 may include 2202 a bottom layer of transistors and wires2202, oxide layer 2204, oxide regions 2206, gate dielectric 2208, n+silicon regions 2210, gate electrode 2212 and region of p− siliconregion 2214. The recessed channel transistor is surrounded onsubstantially all sides by thermally insulating oxide layers oxide layer2204 and oxide regions 2206, and heat removal may be a serious issue.Furthermore, to contact the p− silicon region 2214, a p+ region may beneeded to obtain low contact resistance, which may not be easy toconstruct at temperatures lower than approximately 400° C.

FIG. 17A-D illustrates an embodiment of the invention wherein thermalcontacts can be constructed to a recessed channel transistor. Note thatnumbers used in FIG. 17A-D are inter-related. For example, if a certainnumber is used in FIG. 17A, it has the same meaning if present in FIG.17B. The process flow may begin as illustrated in FIG. 17A with a bottomlayer or layers of transistors and copper interconnects 1702 beingconstructed with a silicon dioxide layer 1704 atop it. Layer transferapproaches similar to those described in U.S. Pat. No. 8,273,610, USpatent publications 2012/0091587 and 2013/0020707, and pending U.S.patent application Ser. Nos. 13/441,923 and 13/099,010 may be utilized.The contents of the foregoing patent and applications are incorporatedherein by reference. An activated layer of p+ silicon 1706, an activatedlayer of p− silicon 1708 and an activated layer of n+ silicon 1710 canbe transferred atop the structure illustrated in FIG. 17A to form thestructure illustrated in FIG. 17B. FIG. 17C illustrates a next step inthe process flow. After forming isolation regions such as, for example,STI-Shallow Trench Isolation (not shown in FIG. 17C for simplicity) andthus forming p+ regions 1707, gate dielectric regions 1716 and gateelectrode regions 1718 could be formed, for example, by etch anddeposition processes, using procedures similar to those described inU.S. Pat. No. 8,273,610, US patent publications 2012/0091587 and2013/0020707, and pending U.S. patent application Ser. Nos. 13/441,923and 13/099,010. Thus, p− silicon region 1712 and n+ silicon regions 1714may be formed. FIG. 17C thus illustrates an RCAT (recessed channeltransistor) formed with a p+ silicon region atop copper interconnectregions where the copper interconnect regions are not exposed totemperatures higher than approximately 400° C. FIG. 17D illustrates anext step of the process where thermal contacts could be made to the p+silicon region 1707. FIG. 17D may include final p− silicon region 1722and final n+ silicon regions 1720. Via 1724 may be etched andconstructed, for example, of metals (such as Cu, Al, W, degeneratelydoped Si), metal silicides (WSi₂) or a combination of the two, and mayinclude oxide isolation regions 1726. Via 1724 can connect p+ region1707 to the ground (GND) distribution network. Via 1724 couldalternatively be connected to a body bias distribution network. Via 1724and final n+ silicon regions 1720 may be electrically coupled, such asby removal of a portion of an oxide isolation regions 1726, if desiredfor circuit reasons (not shown). The nRCAT could have its body regionconnected to GND potential (or body bias circuit) and operate correctlyor as desired, and the heat produced in the device layer can be removedthrough the low-thermal resistance GND distribution network to the heatremoval apparatus (not shown for clarity).

FIG. 18 illustrates an embodiment the invention, which illustrates theapplication of thermal contacts to remove heat from a pRCAT device layerthat is stacked above a bottom layer of transistors and wires 1802. Thep-RCAT layer may include 1804 buried oxide region 1804, n+ siliconregion 1806, n− silicon region 1814, p+ silicon region 1810, gatedielectric 1808 and gate electrode 1812. The structure shown in FIG. 18can be constructed using methods similar to those described in respectto FIG. 17A-D above. The thermal contact 1818 could be constructed of,for example, metals (such as Cu, Al, W, degenerately doped Si), metalsilicides (WSi₂) or a combination of two or more types of materials, andmay include oxide isolation regions 1816. Thermal contact 1818 mayconnect n+ region 1806 to the power (V_(DD)) distribution network. ThepRCAT could have its body region connected to the supply voltage(V_(DD)) potential (or body bias circuit) and operate correctly or asdesired, and the heat produced in the device layer can be removedthrough the low-thermal resistance V_(DD) distribution network to theheat removal apparatus. Thermal contact 1818 could alternatively beconnected to a body bias distribution network (not shown for clarity).Thermal contact 1818 and p+ silicon region 1810 may be electricallycoupled, such as by removal of a portion of an oxide isolation regions1816, if desired for circuit reasons (not shown).

FIG. 19 illustrates an embodiment of the invention that describes theapplication of thermal contacts to remove heat from a CMOS device layerthat could be stacked atop a bottom layer of transistors and wires 1902.The CMOS device layer may include insulator regions 1904, sidewallinsulator regions 1924, thermal via insulator regions 1930, such assilicon dioxide. The CMOS device layer may include nMOS p+ siliconregion 1906, pMOS p+ silicon region 1936, nMOS p− silicon region 1908,pMOS buried p− silicon region 1912, nMOS n+ silicon regions 1910, pMOSn+ silicon 1914, pMOS n− silicon region 1916, p+ silicon regions 1920,pMOS gate dielectric region 1918, pMOS gate electrode region 1922, nMOSgate dielectric region 1934 and nMOS gate electrode region. A nMOStransistor could therefore be formed of regions 1934, 1928, 1910, 1908and 1906. A pMOS transistor could therefore be formed of regions 1914,1916, 1918, 1920 and 1922. This stacked CMOS device layer could beformed with procedures similar to those described in U.S. Pat. No.8,273,610, US patent publications 2012/0091587 and 2013/0020707, andpending U.S. patent application Ser. Nos. 13/441,923 and 13/099,010 andat least FIG. 17A-D herein. The thermal contact 1926 may be connectedbetween n+ silicon region 1914 and the power (V_(DD)) distributionnetwork and helps remove heat from the pMOS transistor. This is becausethe pMOSFET could have its body region connected to the supply voltage(V_(DD)) potential or body bias distribution network and operatecorrectly or as desired, and the heat produced in the device layer canbe removed through the low-thermal resistance V_(DD) distributionnetwork to the heat removal apparatus as previously described. Thethermal contact 1932 may be connected between p+ silicon region 1906 andthe ground (GND) distribution network and helps remove heat from thenMOS transistor. This is because the nMOSFET could have its body regionconnected to GND potential or body bias distribution network and operatecorrectly or as desired, and the heat produced in the device layer canbe removed through the low-thermal resistance GND distribution networkto the heat removal apparatus as previously described.

FIG. 20 illustrates an embodiment of the invention that describes atechnique that could reduce heat-up of transistors fabricated onsilicon-on-insulator (SOI) substrates. SOI substrates have a buriedoxide (BOX) or other insulator between the silicon transistor regionsand the heat sink. This BOX region may have a high thermal resistance,and makes heat transfer from the transistor regions to the heat sinkdifficult. The nMOS transistor in SOI may include buried oxide regions2036, BEOL metal insulator regions 2048, and STI insulator regions 2056,such as silicon dioxide. The nMOS transistor in SOI may include n+silicon regions 2046, p− silicon regions 2040, gate dielectric region2052, gate electrode region 2054, interconnect wiring regions 2044, andhighly doped silicon substrate 2004. Use of silicon-on-insulator (SOI)substrates may lead to low heat transfer from the transistor regions tothe heat removal apparatus 2002 through the buried oxide regions 2036(generally a layer) that may have low thermal conductivity. The groundcontact 2062 of the nMOS transistor shown in FIG. 20 can be connected tothe ground distribution network wiring 2064 which in turn can beconnected with a low thermal resistance connection 2050 to highly dopedsilicon substrate 2004. This enables low thermal conductivity, a thermalconduction path, between the transistor shown in FIG. 20 and the heatremoval apparatus 2002. While FIG. 20 described how heat could betransferred among an nMOS transistor and the heat removal apparatus,similar approaches can also be used for pMOS transistors, and many othertransistors, for example, FinFets, BJTs, HEMTs, and HBTs. Many of theaforementioned transistors may be constructed as fully depleted channeldevices. The heat removal apparatus 2002 may include an external surfacefrom which heat transfer may take place by methods such as air cooling,liquid cooling, or attachment to another heat sink or heat spreaderstructure.

FIG. 21 illustrates an embodiment of the invention which describes atechnique that could reduce heat-up of transistors fabricated onsilicon-on-insulator (SOI) substrates. The nMOS transistor in SOI mayinclude buried oxide regions 2136, BEOL metal insulator regions 2148,and STI insulator regions 2156, such as silicon dioxide. The nMOStransistor in SOI may include n+ silicon regions 2146, p− siliconregions 2140, gate dielectric region 2152, gate electrode region 2154,interconnect wiring regions 2144, and highly doped silicon substrate2104. Use of silicon-on-insulator (SOI) substrates may lead to low heattransfer from the transistor regions to the heat removal apparatus 2102through the buried oxide regions 2136 (generally a layer) that may havelow thermal conductivity. The ground contact 2162 of the nMOS transistorshown in FIG. 21 can be connected to the ground distribution network2164 which in turn can be connected with a low thermal resistanceconnection 2150 to highly doped silicon substrate 2104 through animplanted and activated region 2110. The implanted and activated region2110 could be such that thermal contacts similar to those in FIG. 6 canbe formed. This may enable low thermal conductivity, a thermalconduction path, between the transistor shown in FIG. 21 and the heatremoval apparatus 2102. This thermal conduction path, whilst thermallyconductive, may not be electrically conductive (due to the reversebiased junctions that could be constructed in the path), and thus, notdisturb the circuit operation. While FIG. 21 described how heat could betransferred among the nMOS transistor and the heat removal apparatus,similar approaches can also be used for pMOS transistors, and othertransistors, for example, FinFets, BJTs, HEMTs, and HBTs.

FIG. 23 illustrates an embodiment of the invention wherein heatspreading regions may be located on the sides of 3D-ICs. The 3Dintegrated circuit shown in FIG. 23 could be potentially constructedusing techniques described in U.S. Pat. No. 8,273,610, US patentpublications 2012/0091587 and 2013/0020707, and pending U.S. patentapplication Ser. Nos. 13/441,923 and 13/099,010. For example, twocrystalline layers, 2304 and 2316, which may include semiconductormaterials such as, for example, mono-crystalline silicon, germanium,GaAs, InP, and graphene, are shown. For this illustration,mono-crystalline (single crystal) silicon may be used. Silicon layer2316 could be thinned from its original thickness, and its finalthickness could be in the range of about 0.01 um to about 50 um, forexample, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Siliconlayer 2304 could be thinned down from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um; however,due to strength considerations, silicon layer 2304 may also be ofthicknesses greater than 100 um, depending on, for example, the strengthof bonding to heat removal apparatus 2302. Silicon layer 2304 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 2314, gate dielectricregion 2312, and shallow trench isolation (STI) regions 2310 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). Silicon layer 2316 mayinclude transistors such as, for example, MOSFETS, FinFets, BJTs, HEMTs,HBTs, which may include gate electrode region 2334, gate dielectricregion 2332, and shallow trench isolation (STI) regions 2322 and severalother regions that may be necessary for transistors such as source anddrain junction regions (not shown for clarity). It can be observed thatthe STI regions 2322 can go right through to the bottom of silicon layer2316 and provide good electrical isolation. A through-layer via (TLV)2318 may be present and may include an associated surrounding dielectricregion 2320. Dielectric region 2320 may include a shallow trenchisolation region. Wiring layers 2308 for silicon layer 2304 and wiringdielectric 2306 may be present and may form an associated interconnectlayer or layers. Wiring layers 2338 for silicon layer 2316 and wiringdielectric 2336 may be present and may form an associated interconnectlayer or layers. Through-layer via (TLV) 2318 may connect to wiringlayers 2308 and wiring layers 2338 (not shown). The heat removalapparatus 2302 may include a heat spreader and/or a heat sink. Thermallyconductive material regions 2340 could be present at the sides of the3D-IC shown in FIG. 23 . Thermally conductive material regions 2340 maybe formed by sequential layer by layer etch and fill, or by an end ofprocess etch and fill. Thus, a thermally conductive heat spreadingregion could be located on the sidewalls of a 3D-IC. The thermallyconductive material regions 2340 could include dielectrics such as, forexample, insulating carbon, diamond, diamond like carbon (DLC), andother dielectrics that have a thermal conductivity higher than silicondioxide and/or have a thermal conductivity higher than 0.6 W/m-K.Another method that could be used for forming thermally conductivematerial regions 2340 could involve depositing and planarizing thethermally conductive material at locations on or close to the dicingregions, such as potential dicing scribe lines (described in U.S. PatentApplication Publication 2012/0129301) of a 3D-IC after an etch process.The wafer could be diced. Those of ordinary skill in the art willappreciate that one could combine the concept of having thermallyconductive material regions on the sidewalls of 3D-ICs with conceptsshown in other figures of this patent application, such as, for example,the concept of having lateral heat spreaders shown in FIG. 8 . Siliconlayer 2304 and silicon layer 2316 may be may be substantially absent ofsemiconductor dopants to form an undoped silicon region or layer, ordoped, such as, for example, with elemental or compound species thatform a p+, or p, or p−, or n+, or n, or n− silicon layer or region. Theheat removal apparatus 2302 may include an external surface from whichheat transfer may take place by methods such as air cooling, liquidcooling, or attachment to another heat sink or heat spreader structure.

FIG. 25 illustrates an exemplary monolithic 3D integrated circuit. The3D integrated circuit shown in FIG. 25 could be potentially constructedusing techniques described in U.S. Pat. No. 8,273,610, US patentpublications 2012/0091587 and 2013/0020707, and pending U.S. patentapplication Ser. Nos. 13/441,923 and 13/099,010. For example, twocrystalline layers, 2504 and 2516, which may include semiconductormaterials such as, for example, mono-crystalline silicon, germanium,GaAs, InP, and graphene, are shown. For this illustration,mono-crystalline (single crystal) silicon may be used. Silicon layer2516 could be thinned from its original thickness, and its finalthickness could be in the range of about 0.01 um to about 50 um, forexample, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Siliconlayer 2504 could be thinned down from its original thickness, and itsfinal thickness could be in the range of about 0.01 um to about 50 um,for example, 10 nm, 100 nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um; however,due to strength considerations, silicon layer 2504 may also be ofthicknesses greater than 100 um, depending on, for example, the strengthof bonding to heat removal apparatus 2502. Silicon layer 2504, orsilicon substrate, may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 2514, gate dielectric region 2512, transistor junction regions2510 and several other regions that may be necessary for transistorssuch as source and drain junction regions (not shown for clarity).Silicon layer 2516 may include transistors such as, for example,MOSFETS, FinFets, BJTs, HEMTs, HBTs, which may include gate electroderegion 2534, gate dielectric region 2532, transistor junction regions2530 and several other regions that may be necessary for transistorssuch as source and drain junction regions (not shown for clarity). Athrough-silicon connection 2518, or TLV (through-silicon via) could bepresent and may have a surrounding dielectric region 2520. Surroundingdielectric region 2520 may include a shallow trench isolation (STI)region, such as one of the shallow trench isolation (STI) regionstypically in a 3D integrated circuit stack (not shown). Silicon layer2504 may have wiring layers 2508 and wiring dielectric 2506. Wiringlayers 2508 and wiring dielectric 2506 may form an associatedinterconnect layer or layers. Silicon layer 2516 may have wiring layers2538 and wiring dielectric 2536. Wiring layers 2538 and wiringdielectric 2536 may form an associated interconnect layer or layers.Wiring layers 2538 and wiring layers 2508 may be constructed of copper,aluminum or other materials with bulk resistivity lower than 2.8uohm-cm. The choice of materials for through-silicon connection 2518 maybe challenging. If copper is chosen as the material for through-siliconconnection 2518, the co-efficient of thermal expansion (CTE) mismatchbetween copper and the surrounding mono-crystalline silicon layer 2516may become an issue. Copper has a CTE of approximately 16.7 ppm/K whilesilicon has a CTE of approximately 3.2 ppm/K. This large CTE mismatchmay cause reliability issues and the need for large keep-out zonesaround the through-silicon connection 2518 wherein transistors cannot beplaced. If transistors are placed within the keep-out zone of thethrough-silicon connection 2518, their current-voltage characteristicsmay be different from those placed in other areas of the chip.Similarly, if Aluminum (CTE=23 ppm/K) is used as the material forthrough-silicon connection 2518, its CTE mismatch with the surroundingmono-crystalline silicon layer 2516 could cause large keep-out zones andreliability issues. Silicon layer 2504 and silicon layer 2516 may be maybe substantially absent of semiconductor dopants to form an undopedsilicon region or layer, or doped, such as, for example, with elementalor compound species that form a p+, or p, or p−, or n+, or n, or n−silicon layer or region.

An embodiment of the invention utilizes a material for thethrough-silicon connection 2518 (TSV or TLV) that may have a CTE closerto silicon than, for example, copper or aluminum. The through-siliconconnection 2518 may include materials such as, for example, tungsten(CTE approximately 4.5 ppm/K), highly doped polysilicon or amorphoussilicon or single crystal silicon (CTE approximately 3 ppm/K),conductive carbon, or some other material with CTE less than 15 ppm/K.Wiring layers 2538 and wiring layers 2508 may have materials with CTEgreater than 15 ppm/K, such as, for example, copper or aluminum.

Persons of ordinary skill in the art will appreciate that theillustrations in FIG. 25 are exemplary only and are not drawn to scale.Such skilled persons will further appreciate that many variations arepossible such as, for example, the through-silicon connection 2518 mayinclude materials in addition to those (such as Tungsten, conductivecarbon) described above, for example, liners and barrier metals such asTiN, TaN, and other materials known in the art for via, contact, andthrough silicon via formation. Moreover, the transistors in siliconlayer 2504 may be formed in a manner similar to silicon layer 2516.Furthermore, through-silicon connection 2518 may be physically andelectrically connected (not shown) to wiring layers 2508 and wiringlayers 2538 by the same material as the wiring layers 2508/2538, or bythe same materials as the through-silicon connection 2518 composition,or by other electrically and/or thermally conductive materials not foundin the wiring layers 2508/2538 or the through-silicon connection 2518.Many other modifications within the scope of the invention will suggestthemselves to such skilled persons after reading this specification.Thus the invention is to be limited only by the appended claims.

Alignment is a basic step in semiconductor processing. In most cases itis part of the flow that every successive layer is patterned and alignedto a previous or underneath layer. This alignment of each layer couldall be done to one common alignment mark, such as for example the zeromark utilized by some ASML equipment, or to some other alignment mark ormarks that are embedded in a layer underneath the masking layer beingaligned. In today's equipment such alignment would be precise to below40 nanometers, or 10 nanometers or a few nanometers. In general suchalignment could be observed outside the manufacturing fabricationfacility by comparing two devices processed using the same mask set. Iftwo layers in one device maintain their relative positions the same—tofew nanometers—as the other device, it is a clear indication that theselayers are one aligned to the other. This could be achieve by eitheraligning to the same alignment mark or one is using alignment markembedded in the other or using different alignment marks of layers thatare aligned to each other. Within the manufacturing fabrication facilityalignment may be observed and measured by scanning the post develop, andsometime post etch, alignment structures such as for example fiducialmarks, or box in box, crosses, etc. as understood by those skilled inthe art.

When formation of a 3D-IC is discussed herein, crystalline layers, forexample, two crystalline layers, 2504 and 2516, are utilized to form themonolithic 3D-IC, generally utilizing layer transfer techniques.Similarly, donor layers and acceptor layers of crystalline materialswhich are referred to and utilized in the referenced US patent documentsincluding U.S. Pat. Nos. 8,273,610, 9,099,526, 9,219,005, 8,557,632 and8,581,349 may be utilized to form a monolithic 3D-IC, generallyutilizing layer transfer techniques. The crystalline layers, whetherdonor or acceptor layer, may include regions of compound semiconductors,such as, for example, InP, GaAs, and/or GaN, and regions ofmono-crystalline silicon and/or silicon dioxide. Heterogeneousintegration with short interconnects between the compound semiconductortransistors and the silicon based transistors (such as CMOS) could beenabled by placing or constructing Si—CS hetero-layers into a monolithic3D-IC structure.

One compelling advantage of the Excico's laser annealing machine is itsoutput optical system. This optical system forms a large rectangularwindow of uniform laser energy with less than 10% variation over thesurface to be annealed, and with sharp edges of less than 100 micronbetween the uniform energy and almost no energy as illustrated in FIG.49 of incorporated patent reference U.S. Pat. No. 9,385,058. Accordinglya whole die or even reticle could be exposed in one shot. By setting thewindow size and aligning the laser to the wafer properly, it could allowthe laser annealing process to have the stitching of optical energy,such as pulsed laser exposures, at a desired area, such as the scribestreet, such as for example lines 104, potential dicing line 104-1,potential dicing lines 104-2, in FIG. 10 of incorporated patentreference U.S. Pat. No. 8,273,610 to Or-Bach, et al. Thus, the laserstich may be placed between dies, thereby reducing the risk from unevenexposure at the stitching area affecting any of the desired circuittransistors or elements. Additionally, the window size may be set tocover a multiplicity of dice or tiles, such as end-device 3611 of FIG.36 of incorporated patent reference U.S. Pat. No. 8,273,610 to Or-Bach,et al., which may also have potential dice lines, such as potential dicelines 3602 and/or actual dice lines, such as actual dice lines 3612. Theoptical annealing could be done sequentially across the wafer or insteppings that substantially cover the entire wafer area but spread theheat generation to allow better heat removal. Such spreading of heatgeneration could be done, for example, by scanning the wafer surfacelike a checkerboard, first exposing rectangles or areas such as the‘blacks’ of the checkerboard, and then the ‘white’ locations.

A planar fully depleted n-channel Recessed Channel Array Transistor(FD-RCAT) suitable for a monolithic 3D IC may be constructed as follows.The FD-RCAT may provide an improved source and drain contact resistance,thereby allowing for lower channel doping (such as undoped), and therecessed channel may provide for more flexibility in the engineering ofchannel lengths and transistor characteristics, and increased immunityfrom process variations. The buried doped layer and channel dopantshaping, even to an un-doped channel, may allow for efficient adaptiveand dynamic body biasing to control the transistor threshold andthreshold variations, as well as provide for a fully depleted or deeplydepleted transistor channel. Furthermore, the recessed gate allows foran FD transistor but with thicker silicon for improved lateral heatconduction. FIG. 26A-F illustrates an exemplary re-channel FD-RCAT whichmay be constructed in a 3D stacked layer using procedures outlined belowand in U.S. Pat. Nos. 8,273,610, 9,099,526, 9,219,005, 8,557,632 and8,581,349. The contents of the foregoing patent and applications areincorporated herein by reference.

As illustrated in FIG. 26A, a P− substrate donor wafer 2600 may beprocessed to include wafer sized layers of N+ doping 2602, P− doping2606, channel 2603 and P+ doping 2604 across the wafer. The N+ dopedlayer 2602, P− doped layer 2606, channel layer 2603 and P+ doped layer2604 may be formed by ion implantation and thermal anneal. P− substratedonor wafer 2600 may include a crystalline material, for example,mono-crystalline (single crystal) silicon. P− doped layer 2606 andchannel layer 2603 may have additional ion implantation and annealprocessing to provide a different dopant level than P− substrate donorwafer 2600. P− substrate donor wafer 2600 may be very lightly doped(less than 1e15 atoms/cm³) or nominally un-doped (less than 1e14atoms/cm³). P− doped layer 2606, channel layer 2603, and P+ doped layer2604 may have graded or various layers doping to mitigate transistorperformance issues, such as, for example, short channel effects, afterthe FD-RCAT is formed, and to provide effective body biasing, whetheradaptive or dynamic. The layer stack may alternatively be formed bysuccessive epitaxially deposited doped silicon layers of N+ doped layer2602, P− doped layer 2606, channel layer 2603 and P+ doped layer 2604,or by a combination of epitaxy and implantation. Annealing of implantsand doping may include, for example, conductive/inductive thermal,optical annealing techniques or types of Rapid Thermal Anneal (RTA orspike). The N+ doped layer 2602 may have a doping concentration that maybe more than 10× the doping concentration of P− doped layer 2606 and/orchannel layer 2603. The P+ doped layer 2604 may have a dopingconcentration that may be more than 10× the doping concentration of P−doped layer 2606 and/or channel layer 2603. The P− doped layer 2606 mayhave a doping concentration that may be more than 10× the dopingconcentration of channel layer 2603. Channel layer 2603 may have athickness and/or doping that may allow fully-depleted channel operationwhen the FD-RCAT transistor is substantially completely formed, such as,for example, less than 5 nm, less than 10 nm, or less than 20 nm.

As illustrated in FIG. 26B, the top surface of the P− substrate donorwafer 2600 layer stack may be prepared for oxide wafer bonding with adeposition of an oxide or by thermal oxidation of P+ doped layer 2604 toform oxide layer 2680. A layer transfer demarcation plane (shown asdashed line) 2699 may be formed by hydrogen implantation or othermethods as described in the incorporated references. The P− substratedonor wafer 2600 and acceptor wafer 2610 may be prepared for waferbonding as previously described and low temperature (less thanapproximately 400° C.) bonded. Acceptor wafer 2610, as described in theincorporated references, may include, for example, transistors,circuitry, and metal, such as, for example, aluminum or copper,interconnect wiring, a metal shield/heat sink layer, and thru layer viametal interconnect strips or pads. Acceptor wafer 2610 may besubstantially comprised of a crystalline material, for examplemono-crystalline silicon or germanium, or may be an engineeredsubstrate/wafer such as, for example, an SOI (Silicon on Insulator)wafer or GeOI (Germanium on Insulator) substrate. The portion of the N+doped layer 2602 and the P− substrate donor wafer 2600 that may be above(when the layer stack is flipped over and bonded to the acceptor wafer)the layer transfer demarcation plane 2699 may be removed by cleaving orother low temperature processes as described in the incorporatedreferences, such as, for example, ion-cut or other layer transfermethods.

As illustrated in FIG. 26C, oxide layer 2680, P+ doped layer 2604,channel layer 2603, P− doped layer 2606, and remaining N+ layer 2622have been layer transferred to acceptor wafer 2610. The top surface ofN+ layer 2622 may be chemically or mechanically polished. Nowtransistors may be formed with low effective temperature (less thanapproximately 400° C. exposure to the acceptor wafer 2610 sensitivelayers, such as interconnect and device layers) processing and alignedto the acceptor wafer alignment marks (not shown) as described in theincorporated references.

As illustrated in FIG. 26D, the transistor isolation regions 2605 may beformed by mask defining and plasma/RIE etching remaining N+ layer 2622,P− doped layer 2606, channel layer 2603, and P+ doped layer 2604substantially to the top of oxide layer 2680 (not shown), substantiallyinto oxide layer 2680, or into a portion of the upper oxide layer ofacceptor wafer 2610 (not shown). Additionally, a portion of thetransistor isolation regions 2605 may be etched (separate step)substantially to P+ doped layer 2604, thus allowing multiple transistorregions to be connected by the same P+ doped region 2624. Alow-temperature gap fill oxide may be deposited and chemicallymechanically polished, the oxide remaining in isolation regions 2605.The recessed channel 2686 may be mask defined and etched thru remainingN+ doped layer 2622, P− doped layer 2606 and partially into channellayer 2603. The recessed channel surfaces and edges may be smoothed byprocesses, such as, for example, wet chemical, plasma/RIE etching, lowtemperature hydrogen plasma, or low temperature oxidation and striptechniques, to mitigate high field effects. The low temperaturesmoothing process may employ, for example, a plasma produced in a TEL(Tokyo Electron Labs) SPA (Slot Plane Antenna) machine. Thus N+ sourceand drain regions 2632, P− regions 2626, and channel region 2623 may beformed, which may substantially form the transistor body. The dopingconcentration of N+ source and drain regions 2632 may be more than 10×the concentration of channel region 2623. The doping concentration ofthe N− channel region 2623 may include gradients of concentration orlayers of differing doping concentrations. The doping concentration ofN+ source and drain regions 2632 may be more than 10× the concentrationof P− regions 2626. The etch formation of recessed channel 2686 maydefine the transistor channel length. The shape of the recessed etch maybe rectangular as shown, or may be spherical (generally from wetetching, sometimes called an S-RCAT: spherical RCAT), or a variety ofother shapes due to etching methods and shaping from smoothingprocesses, and may help control for the channel electric fielduniformity. The thickness of channel region 2623 in the region belowrecessed channel 2686 may be of a thickness that allows fully-depletedchannel operation. The thickness of channel region 2623 in the regionbelow N+ source and drain regions 2632 may be of a thickness that allowsfully-depleted transistor operation.

As illustrated in FIG. 26E, a gate dielectric 2607 may be formed and agate metal material may be deposited. The gate dielectric 2607 may be anatomic layer deposited (ALD) gate dielectric that may be paired with awork function specific gate metal in the industry standard high k metalgate process schemes described in the incorporated references.Alternatively, the gate dielectric 2607 may be formed with a lowtemperature processes including, for example, LPCVD SiO₂ oxidedeposition or low temperature microwave plasma oxidation of the siliconsurfaces and a gate material with proper work function and less thanapproximately 400° C. deposition temperature such as, for example,tungsten or aluminum may be deposited. The gate material may bechemically mechanically polished, and the gate area defined by maskingand etching, thus forming the gate electrode 2608. The shape of gateelectrode 2608 is illustrative; the gate electrode may also overlap aportion of N+ source and drain regions 2632.

As illustrated in FIG. 26F, a low temperature thick oxide 2609 may bedeposited and planarized, and source, gate, and drain contacts, P+ dopedregion contact (not shown) and thru layer via (not shown) openings maybe masked and etched preparing the transistors to be connected viametallization. P+ doped region contact may be constructed thru isolationregions 2605, suitably when the isolation regions 2605 is formed to ashared P+ doped region 2624. Thus gate contact 2611 connects to gateelectrode 2608, and source & drain contacts 2640 connect to N+ sourceand drain regions 2632. The thru layer via (not shown) provideselectrical coupling among the donor wafer transistors and the acceptorwafer metal connect pads or strips (not shown) as described in theincorporated references.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 26A through 26F are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations are possible such as, for example, a p-channel FD-RCAT may beformed with changing the types of dopings appropriately. Moreover, theP− substrate donor wafer 2600 may be n type or un-doped. Further, P−doped channel layer 2603 may include multiple layers of different dopingconcentrations and gradients to fine tune the eventual FD-RCAT channelfor electrical performance and reliability characteristics, such as, forexample, off-state leakage current and on-state current. Furthermore,isolation regions 2605 may be formed by a hard mask defined processflow, wherein a hard mask stack, such as, for example, silicon oxide andsilicon nitride layers, or silicon oxide and amorphous carbon layers,may be utilized. Moreover, CMOS FD-RCATs may be constructed withn-JLRCATs in a first mono-crystalline silicon layer and p-JLRCATs in asecond mono-crystalline layer, which may include different crystallineorientations of the mono-crystalline silicon layers, such as forexample, <100>, <111> or <551>, and may include different contactsilicides for optimum contact resistance to p or n type source, drains,and gates. Furthermore, P+ doped regions 2624 may be utilized for adouble gate structure for the FD-RCAT and may utilize techniquesdescribed in the incorporated references. Further, efficient heatremoval and transistor body biasing may be accomplished on a FD-RCAT byadding an appropriately doped buried layer (N− in the case of an-FD-RCAT), forming a buried layer region underneath the P+ doped region2624 for junction isolation, and connecting that buried region to athermal and electrical contact, similar to what is described for layer1606 and region 1646 in FIGS. 16A-G in the incorporated referencepending U.S. patent application Ser. No. 13/441,923 and U.S. PatentPublication 2012/0091587. Many other modifications within the scope ofthe invention will suggest themselves to such skilled persons afterreading this specification. Thus the invention is to be limited only bythe appended claims.

Defect annealing, such as furnace thermal or optical annealing, of thinlayers of the crystalline materials generally included in 3D-ICs to thetemperatures that may lead to substantial dopant activation or defectanneal, for example above 600° C., may damage or melt the underlyingmetal interconnect layers of the stacked 3D-IC, such as copper oraluminum interconnect layers. An embodiment of the invention is to form3D-IC structures and devices wherein a heat spreading, heat conductingand/or optically reflecting or absorbent material layer or layers (whichmay be called a shield) is incorporated between the sensitive metalinterconnect layers and the layer or regions being optically irradiatedand annealed, or annealed from the top of the 3D-IC stack using othermethods. An exemplary generalized process flow is shown in FIGS. 27A-F.An exemplary process flow for an FD-RCAT with an optional integratedheat shield/spreader is shown in FIGS. 28A-G. An exemplary process flowfor a FD-MOSFET with an optional integrated heat shield/spreader isshown in FIGS. 29A-G. An exemplary process flow for a planar fullydepleted n-channel MOSFET (FD-MOSFET) with an optional integrated heatshield/spreader and back planes and body bias taps is shown in FIGS.30A-G. An exemplary process flow for a horizontally oriented JFET or JLTwith an optional integrated heat shield/spreader is shown in FIGS.31A-G. The 3D-ICs may be constructed in a 3D stacked layer usingprocedures outlined herein (such as, for example, FIGS. 39, 40, 41 ofincorporated patent reference U.S. Pat. No. 9,385,058) and in U.S. Pat.Nos. 8,273,610, 9,099,526, 9,219,005, 8,557,632 and 8,581,349. Thecontents of the foregoing applications are incorporated herein byreference. The topside defect anneal may include optical annealing torepair defects in the crystalline 3D-IC layers and regions (which may becaused by the ion-cut implantation process), and may be utilized toactivate semiconductor dopants in the crystalline layers or regions of a3D-IC, such as, for example, LDD, halo, source/drain implants. The 3D-ICmay include, for example, stacks formed in a monolithic manner with thinlayers or stacks and vertical connection such as TLVs, and stacks formedin an assembly manner with thick (>2 um) layers or stacks and verticalconnections such as TSVs. Optical annealing beams or systems, such as,for example, a laser-spike anneal beam from a commercial semiconductormaterial oriented single or dual-beam continuous wave (CW) laser spikeanneal DB-LSA system of Ultratech Inc., San Jose, Calif., USA (10.6 umlaser wavelength), or a short pulse laser (such as 160 ns), with 308 nmwavelength, and large area (die or step-field sized, including 1 cm²)irradiation such as offered by Excico of Gennevilliers, France, may beutilized (for example, see Huet, K., “Ultra Low Thermal Budget LaserThermal Annealing for 3D Semiconductor and Photovoltaic Applications,”NCCAVS 2012 Junction Technology Group, Semicon West, San Francisco, Jul.12, 2012). Additionally, the defect anneal may include, for example,laser anneals (such as suggested in Rajendran, B., “Sequential 3D ICFabrication: Challenges and Prospects”, Proceedings of VLSI Multi LevelInterconnect Conference 2006, pp. 57-64), Ultrasound Treatments (UST),megasonic treatments, and/or microwave treatments. The topside defectanneal ambient may include, for example, vacuum, high pressure (greaterthan about 760 torr), oxidizing atmospheres (such as oxygen or partialpressure oxygen), and/or reducing atmospheres (such as nitrogen orargon). The topside defect anneal may include temperatures of the layerbeing annealed above about 400° C. (a high temperature thermal anneal),including, for example, 600° C., 800° C., 900° C., 1000° C., 1050° C.,1100° C. and/or 1120° C., and the sensitive metal interconnect (forexample, may be copper or aluminum containing) and/or device layersbelow may not be damaged by the annealing process, for example, whichmay include sustained temperatures that do not exceed 200° C., exceed300° C., exceed 370° C., or exceed 400° C. As understood by those ofordinary skill in the art, short-timescale (nanosceonds to miliseconds)temperatures above 400° C. may also be acceptable for damage avoidance,depending on the acceptor layer interconnect metal systems used. Thetopside defect anneal may include activation of semiconductor dopants,such as, for example, ion implanted dopants or PLAD applied dopants. Itwill also be understood by one of ordinary skill in the art that themethods, such as the heat sink/shield layer and/or use of short pulseand short wavelength optical anneals, may allow almost any type oftransistor, for example, such as FinFets, bipolar, nanowire transistors,to be constructed in a monolithic 3D fashion as the thermal limit ofdamage to the underlying metal interconnect systems is overcome.Moreover, multiple pulses of the laser, other optical annealingtechniques, or other anneal treatments such as microwave, may beutilized to improve the anneal, activation, and yield of the process.The transistors formed as described herein may include many types ofmaterials; for example, the channel and/or source and drain may includesingle crystal materials such as silicon, germanium, or compoundsemiconductors such as GaAs, InP, GaN, SiGe, and although the structuresmay be doped with the tailored dopants and concentrations, they maystill be substantially crystalline or mono-crystalline.

As illustrated in FIG. 27A, a generalized process flow may begin with adonor wafer 2700 that may be preprocessed with wafer sized layers 2702of conducting, semi-conducting or insulating materials that may beformed by deposition, ion implantation and anneal, oxidation, epitaxialgrowth, combinations of above, or other semiconductor processing stepsand methods. For example, donor wafer 2700 and wafer sized layers 2702may include semiconductor materials such as, for example,mono-crystalline silicon, germanium, GaAs, InP, and graphene. For thisillustration, mono-crystalline (single crystal) silicon and associatedsilicon oriented processing may be used. The donor wafer 2700 may bepreprocessed with a layer transfer demarcation plane (shown as dashedline) 2799, such as, for example, a hydrogen implant cleave plane,before or after (typical) wafer sized layers 2702 are formed. Layertransfer demarcation plane 2799 may alternatively be formed within wafersized layers 2702. Other layer transfer processes, some described in thereferenced patent documents, may alternatively be utilizedDamage/defects to the crystalline structure of donor wafer 2700 may beannealed by some of the annealing methods described, for example theshort wavelength pulsed laser techniques, wherein the donor wafer 2700wafer sized layers 2702 and portions of donor wafer 2700 may be heatedto defect annealing temperatures, but the layer transfer demarcationplane 2799 may be kept below the temperate for cleaving and/orsignificant hydrogen diffusion. Dopants in at least a portion of wafersized layers 2702 may also be electrically activated. Thru theprocessing, donor wafer 2700 and/or wafer sized layers 2702 could bethinned from its original thickness, and their/its final thickness couldbe in the range of about 0.01 um to about 50 um, for example, 10 nm, 100nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Donor wafer 2700 and wafer sizedlayers 2702 may include preparatory layers for the formation ofhorizontally or vertically oriented types of transistors such as, forexample, MOSFETS, FinFets, FD-RCATs, BJTs, HEMTs, HBTs, JFETs, JLTs, orpartially processed transistors (for example, the replacement gate HKMGprocess described in the referenced patent documents). Donor wafer 2700and wafer sized layers 2702 may include the layer transfer devicesand/or layer or layers contained herein this document or referencedpatent documents, for example, DRAM Si/SiO₂ layers, RCAT doped layers,multi-layer doped structures, or starting material doped or undopedmonocrystalline silicon, or polycrystalline silicon. Donor wafer 2700and wafer sized layers 2702 may have alignment marks (not shown).Acceptor wafer 2710 may be a preprocessed wafer, for example, includingmonocrystalline bulk silicon or SOI, that may have fully functionalcircuitry including metal layers (including aluminum or copper metalinterconnect layers that may connect acceptor wafer 2710 transistors andmetal structures, such as TLV landing strips and pads, prepared toconnect to the transferred layer devices) or may be a wafer withpreviously transferred layers, or may be a blank carrier or holderwafer, or other kinds of substrates suitable for layer transferprocessing. Acceptor wafer 2710 may have alignment marks 2790 and metalconnect pads or strips 2780 and ray blocked metal interconnect 2781.Acceptor wafer 2710 may include transistors such as, for example,MOSFETS, FinFets, FD-RCATs, BJTs, JFETs, JLTs, HEMTs, and/or HBTs.Acceptor wafer 2710 may include shield/heat sink layer 2788, which mayinclude materials such as, for example, Aluminum, Tungsten (a refractorymetal), Copper, silicon or cobalt based silicides, or forms of carbonsuch as carbon nanotubes or DLC (Diamond Like Carbon), and may belayered itself as described in FIG. 50 of incorporated patent referenceU.S. Pat. No. 9,385,058. Shield/heat sink layer 2788 may have athickness range of about 50 nm to about 1 mm, for example, 50 nm, 100nm, 200 nm, 300 nm, 500 nm, 0.1 um, 1 um, 2 um, and 10 um. Shield/heatsink layer 2788 may include isolation openings 2786, and alignment markopenings 2787, which may be utilized for short wavelength alignment oftop layer (donor) processing to the acceptor wafer alignment marks 2790.Shield/heat sink layer 2788 may include shield path connect 2785 andshield path via 2783. Shield path via 2783 may thermally and/orelectrically couple and connect shield path connect 2785 to acceptorwafer 2710 interconnect metallization layers such as, for example, metalconnect pads or strips 2780 (shown). If two shield/heat sink layers 2788are utilized, one on top of the other and separated by an isolationlayer common in semiconductor BEOL, such as carbon doped silicon oxide,shield path connect 2785 may also thermally and/or electrically coupleand connect each shield/heat sink layer 2788 to the other and toacceptor wafer 2710 interconnect metallization layers such as, forexample, metal connect pads or strips 2780, thereby creating a heatconduction path from the shield/heat sink layer 2788 to the acceptorwafer substrate, and a heat sink (shown in FIG. 27F). The topmostshield/heat sink layer may include a higher melting point material, forexample a refractory metal such as Tungsten, and the lower heat shieldlayer may include a lower melting point material such as copper.

As illustrated in FIG. 27B, two exemplary top views of shield/heat sinklayer 2788 are shown. In shield/heat sink portion 2720 a shield area2722 of the shield/heat sink layer 2788 materials described above and inthe incorporated references may include TLV/TSV connects 2724 andisolation openings 2786. Isolation openings 2786 may be the absence ofthe material of shield area 2722. TLV/TSV connects 2724 are an exampleof a shield path connect 2785. TLV/TSV connects 2724 and isolationopenings 2786 may be drawn in the database of the 3D-IC stack and mayformed during the acceptor wafer 2710 processing. In shield/heat sinkportion 2730 a shield area 2732 of the shield/heat sink layer 2788materials described above and in the incorporated references may havemetal interconnect strips 2734 and isolation openings 2786. Metalinterconnect strips 2734 may be surrounded by regions, such as isolationopenings 2786, where the material of shield area 2732 may be etchedaway, thereby stopping electrical conduction from metal interconnectstrips 2734 to shield area 2732 and to other metal interconnect strips.Metal interconnect strips 2734 may be utilized to connect/couple thetransistors formed in the donor wafer layers, such as 2702, tothemselves from the ‘backside’ or ‘underside’ and/or to transistors inthe acceptor wafer level/layer. Metal interconnect strips 2734 andshield/heat sink layer 2788 regions such as shield area 2722 and shieldarea 2732 may be utilized as a ground plane for the transistors above itresiding in the donor wafer layer or layers and/or may be utilized aspower supply or back-bias, such as Vdd or Vsb, for the transistors aboveit residing in the transferred donor wafer layer or layers. The stripsand/or regions of shield/heat sink layer 2788 may be controlled bysecond layer transistors when supplying power or other signals such asdata or control. For example, as illustrated in FIG. 27B-1 , the topmostshield/heat sink layer 2788 may include a topmost shield/heat sinkportion 2770, which may be configured as fingers or stripes ofconductive material, such as top strips 2774 and strip isolation spaces2776, which may be utilized, for example, to provide back-bias, power,or ground to the second layer transistors above it residing in the donorwafer layer or layers (for example donor wafer device structures 2750).A second shield/heat sink layer 2788, below the topmost shield/heat sinklayer, may include a second shield/heat sink portion 2772, which may beconfigured as fingers or stripes of conductive material, such as secondstrips 2778 and strip isolation spaces 2776, may be oriented in adifferent direction (although not necessarily so) than the topmoststrips, and may be utilized, for example, to provide back-bias, power,or ground to the second layer transistors above it residing in the donorwafer layer or layers (for example donor wafer device structures 2750).Openings, such as opening 2779, in the topmost shield/heat sink layermay be designed to allow connection from the second layer of transistorsto the second shield/heat sink layer, such as from donor wafer devicestructures 2750 to second strips 2778. The strips or fingers may beillustrated as orthogonally oriented layer to layer, but may also takeother drawn shapes and forms; for example, such as diagonal runningshapes as in the X-architecture, overlapping parallel strips, and so on.The portions of the shield/heat sink layer 2788 or layers may include acombination of the strip/finger shapes of FIG. 27B-1 and the illustratedvia connects and fill-in regions of FIG. 27B.

Bonding surfaces, donor bonding surface 2701 and acceptor bondingsurface 2711, may be prepared for wafer bonding by depositions (such assilicon oxide), polishes, plasma, or wet chemistry treatments tofacilitate successful wafer to wafer bonding. The insulation layer, suchas deposited bonding oxides and/or before bonding preparation existingoxides, between the donor wafer transferred layer and the acceptor wafertopmost metal layer, may include thicknesses of less than 1 um, lessthan 500 nm, less than 400 nm, less than 300 nm, less than 200 nm, orless than 100 nm.

As illustrated in FIG. 27C, the donor wafer 2700 with wafer sized layers2702 and layer transfer demarcation plane 2799 may be flipped over,aligned, and bonded to the acceptor wafer 2710. The donor wafer 2700with wafer sized layers 2702 may have alignment marks (not shown).Various topside defect anneals may be utilized. For this illustration,an optical beam such as the laser annealing previously described isused. Optical anneal beams may be optimized to focus light absorptionand heat generation at or near the layer transfer demarcation plane(shown as dashed line) 2799 to provide a hydrogen bubble cleave withexemplary cleave ray 2751. The laser assisted hydrogen bubble cleavewith the absorbed heat generated by exemplary cleave ray 2751 may alsoinclude a pre-heat of the bonded stack to, for example, about 100° C. toabout 400° C., and/or a thermal rapid spike to temperatures above about200° C. to about 600° C. The laser assisted ion-cut cleave may provide asmoother cleave surface upon which better quality transistors may bemanufactured. Reflected ray 2753 may be reflected and/or absorbed byshield/heat sink layer 2788 regions thus blocking the optical absorptionof ray blocked metal interconnect 2781 and potentially enhancing theefficiency of optical energy absorption of the wafer sized layers 2702.Additionally, shield/heat sink layer 2788 may laterally spread andconduct the heat generated by the topside defect anneal, and inconjunction with the dielectric materials (low heat conductivity) aboveand below shield/heat sink layer 2788, keep the interconnect metals andlow-k dielectrics of the acceptor wafer interconnect layers cooler thana damage temperature, such as, for example, 400° C. Annealing of dopantsor annealing of damage, such as from the H cleave implant damage, may beaccomplished by optical annealing rays, such as repair ray 2755. A smallportion of the optical energy, such as unblocked ray 2757, may hit andheat, or be reflected, by (a few rays as the area of the heat shieldopenings, such as 2724, is small compared to the die or device area)such as metal connect pads or strips 2780. Heat generated by absorbedphotons from, for example, cleave ray 2751, reflected ray 2753, and/orrepair ray 2755 may also be absorbed by shield/heat sink layer 2788regions and dissipated laterally and may keep the temperature ofunderlying metal layers, such as ray blocked metal interconnect 2781,and other metal layers below it, cooler and prevent damage. Shield/heatsink layer 2788 may act as a heat spreader. A second layer ofshield/heat sink layer 2788 (not shown) may have been constructed(during the acceptor wafer 2710 formation) with a low heat conductivematerial sandwiched between the two heat sink layers, such as siliconoxide or carbon doped ‘low-k’ silicon oxides, for improved thermalprotection of the acceptor wafer interconnect layers, metal anddielectrics. Electrically conductive materials may be used for the twolayers of shield/heat sink layer 2788 and thus may provide, for example,a Vss and a Vdd plane and/or grid for power delivery that may beconnected to the donor layer transistors above, as well may be connectedto the acceptor wafer transistors below. Shield/heat sink layer 2788 mayinclude materials with a high thermal conductivity greater than 10W/m-K, for example, copper (about 400 W/m-K), aluminum (about 237W/m-K), Tungsten (about 173 W/m-K), Plasma Enhanced Chemical VaporDeposited Diamond Like Carbon-PECVD DLC (about 1000 W/m-K), and ChemicalVapor Deposited (CVD) graphene (about 5000 W/m-K). Shield/heat sinklayer 2788 may be sandwiched and/or substantially enclosed by materialswith a low thermal conductivity less than 10 W/m-K, for example, silicondioxide (about 1.4 W/m-K). The sandwiching of high and low thermalconductivity materials in layers, such as shield/heat sink layer 2788and under & overlying dielectric layers, spreads the localizedheat/light energy of the topside anneal laterally and protect theunderlying layers of interconnect metallization & dielectrics, such asin the acceptor wafer, from harmful temperatures or damage. Further,absorber layers or regions, for example, including amorphous carbon,amorphous silicon, and phase changing materials (see U.S. Pat. Nos.6,635,588 and 6,479,821 to Hawryluk et al. for example), may be utilizedto increase the efficiency of the optical energy capture in conversionto heat for the desired annealing or activation processes. Photoresistmay also be utilized to attenuate the optical energy. For example,pre-processed layers 2702 may include a layer or region of opticalabsorbers such as transferred absorber region 2775, acceptor wafer 2710may include a layer or region of optical absorbers such as acceptorabsorber region 2773, and second device layer 2705 may include a layeror region of optical absorbers such as post transfer absorber regions2777 (shown in FIG. 27E). Transferred absorber region 2775, acceptorabsorber region 2773, and/or post transfer absorber regions 2777 may bepermanent (could be found within the device when manufacturing iscomplete) or temporary so is removed during the manufacturing process.

As illustrated in FIG. 27D, the donor wafer 2700 may be cleaved at orthinned to (or past, not shown) the layer transfer demarcation plane2799, leaving donor wafer portion 2703 and the pre-processed layers 2702bonded to the acceptor wafer 2710, by methods such as, for example,ion-cut or other layer transfer methods. The layer transfer demarcationplane 2799 may instead be placed in the pre-processed layers 2702.Optical anneal beams, in conjunction with reflecting layers and regionsand absorbing enhancement layers and regions, may be optimized to focuslight absorption and heat generation within or at the surface of donorwafer portion 2703 and provide surface smoothing and/or defect annealing(defects may be from the cleave and/or the ion-cut implantation), and/orpost ion-implant dopant activation with exemplary smoothing/annealingray 2766. The laser assisted smoothing/annealing with the absorbed heatgenerated by exemplary smoothing/annealing ray 2766 may also include apre-heat of the bonded stack to, for example, about 100° C. to about400° C., and/or a thermal rapid spike to temperatures above about 200°C. to about 600° C. Moreover, multiple pulses of the laser may beutilized to improve the anneal, activation, and yield of the process.Reflected ray 2763 may be reflected and/or absorbed by shield/heat sinklayer 2788 regions thus blocking the optical absorption of ray blockedmetal interconnect 2781. Annealing of dopants or annealing of damage,such as from the H cleave implant damage, may be also accomplished by aset of rays such as repair ray 2765. A small portion of the opticalenergy, such as unblocked ray 2767, may hit and heat, or be reflected,by a few rays (as the area of the heat shield openings, such as 2724, issmall) such as metal connect pads or strips 2780. Heat generated byabsorbed photons from, for example, smoothing/annealing ray 2766,reflected ray 2763, and/or repair ray 2765 may also be absorbed byshield/heat sink layer 2788 regions and dissipated laterally and maykeep the temperature of underlying metal layers, such as ray blockedmetal interconnect 2781, and other metal layers below it, cooler andprevent damage. A second layer of shield/heat sink layer 2788 may beconstructed with a low heat conductive material sandwiched between thetwo heat sink layers, such as silicon oxide or carbon doped ‘low-k’silicon oxides, for improved thermal protection of the acceptor waferinterconnect layers, metal and dielectrics. Shield/heat sink layer 2788may act as a heat spreader. When there may be more than one shield/heatsink layer 2788 in the device, the heat conducting layer closest to thesecond crystalline layer may be constructed with a different material,for example a high melting point material, for example a refractorymetal such as tungsten, than the other heat conducting layer or layers,which may be constructed with, for example, a lower melting pointmaterial such as aluminum or copper. Electrically conductive materialsmay be used for the two layers of shield/heat sink layer 2788 and thusmay provide, for example, a Vss and a Vdd plane and/or grid that may beconnected to the donor layer transistors above, as well may be connectedto the acceptor wafer transistors below. Noise on the power grids, suchas the Vss and Vdd plane power conducting lines/wires, may be mitigatedby attaching/connecting decoupling capacitors onto the power conductinglines of the grids. The decoupling caps, which may be within the secondlayer (donor, for example, donor wafer device structures 2750) or firstlayer (acceptor, for example acceptor wafer transistors and devices2793), may include, for example, trench capacitors such as described byPei, C., et al., “A novel, low-cost deep trench decoupling capacitor forhigh-performance, low-power bulk CMOS applications,” ICSICT (9^(th)International Conference on Solid-State and Integrated-CircuitTechnology) 2008, October 2008, pp. 1146-1149, of IBM. The decouplingcapacitors may include, for example, planar capacitors, such as poly tosubstrate or poly to poly, or MiM capacitors (Metal-Insulator-Metal).Furthermore, some or all of the layers utilized as shield/heat sinklayer 2788, which may include shapes of material such as the strips orfingers as illustrated in FIG. 27B-1 , may be driven by a portion of thesecond layer transistors and circuits (within the transferred donorwafer layer or layers) or the acceptor wafer transistors and circuits,to provide a programmable back-bias to at least a portion of the secondlayer transistors. The programmable back bias may utilize a circuit todo so, for example, such as shown in FIG. 17B of U.S. Pat. No.8,273,610, the contents incorporated herein by reference; wherein the‘Primary’ layer may be the second layer of transistors for which theback-bias is being provided, the ‘Foundation’ layer could be either thesecond layer transistors (donor) or first layer transistors (acceptor),and the routing metal lines connections 1723 and 1724 may includeportions of the shield/heat sink layer 2788 layer or layers. Moreover,some or all of the layers utilized as shield/heat sink layer 2788, whichmay include strips or fingers as illustrated in FIG. 27B-1 , may bedriven by a portion of the second layer transistors and circuits (withinthe transferred donor wafer layer or layers) or the acceptor wafertransistors and circuits to provide a programmable power supply to atleast a portion of the second layer transistors. The programmable powersupply may utilize a circuit to do so, for example, such as shown inFIG. 17C of U.S. Pat. No. 8,273,610, the contents incorporated herein byreference; wherein the ‘Primary’ layer may be the second layer oftransistors for which the programmable power supplies are being providedto, the ‘Foundation’ layer could be either the second layer transistors(donor) or first layer transistors (acceptor), and the routing metalline connections from Vout to the various second layer transistors mayinclude portions of the shield/heat sink layer 2788 layer or layers. TheVsupply on line 17C12 and the control signals on control line 17C16 maybe controlled by and/or generated in the second layer transistors(donor, for example donor wafer device structures 2750) or first layertransistors (acceptor, for example acceptor wafer transistors anddevices 2793), or off chip circuits. Furthermore, some or all of thelayers utilized as shield/heat sink layer 2788, which may include stripsor fingers as illustrated in FIG. 27B-1 or other shapes such as those inFIG. 27B, may be utilized to distribute independent power supplies tovarious portions of the second layer transistors (donor, for exampledonor wafer device structures 2750) or first layer transistors(acceptor, for example acceptor wafer transistors and devices 2793) andcircuits; for example, one power supply and/or voltage may be routed tothe sequential logic circuits of the second layer and a different powersupply and/or voltage routed to the combinatorial logic circuits of thesecond layer. Moreover, the power distribution circuits/grid may bedesigned so that Vdd may have a different value for each stack layer.Patterning of shield/heat sink layer 2788 or layers can impact theirheat-shielding capacity. This impact may be mitigated, for example, byenhancing the top shield/heat sink layer 2788 areal density, creatingmore of the secondary shield/heat sink layers 2788, or attending tospecial CAD rules regarding their metal density, similar to CAD rulesthat are required to accommodate Chemical-Mechanical Planarization(CMP). These constraints would be integrated into a design and layoutEDA tool. Moreover, the second layer of circuits and transistors, forexample, donor wafer device structures 2750, may include I/O logicdevices, such as SerDes (Serialiser/Deserialiser), and conductive bondpads (not shown). The output or input conductive pads of the I/Ocircuits may be coupled, for example by bonded wires, to externaldevices. The output or input conductive pads may also act as a contactport for the 3D device output to connect to external devices. The emfgenerated by the I/O circuits could be shielded from the other layers inthe stack by use of, for example, the heat shield/heat sink layer 2788.Placement of the I/O circuits on the same stack layer as the conductivebond pad may enable close coupling of the desired I/O energy and lowersignal loss. Furthermore, the second layer of circuits and transistors,for example, donor wafer device structures 2750, may include RF (RadioFrequency) circuits and/or at least one antenna. For example, the secondlayer of circuits and transistors, for example, donor wafer devicestructures 2750, may include RF circuits to enable an off-chipcommunication capability to external devices, for example, a wirelesscommunication circuit or circuits such as a Bluetooth protocol orcapacitive coupling. The emf generated by the RF circuits could beshielded from the other layers in the stack by use of, for example, theheat shield/heat sink layer 2788.

As illustrated in FIG. 27E, the remaining donor wafer portion 2703 maybe removed by polishing or etching and the transferred layers 2702 maybe further processed to create second device layer 2705 which mayinclude donor wafer device structures 2750 and metal interconnect layers(such as second device layer metal interconnect 2761) that may beprecisely aligned to the acceptor wafer alignment marks 2790. Donorwafer device structures 2750 may include, for example, CMOS transistorssuch as N type and P type transistors, or at least any of the othertransistor or device types discussed herein this document or referencedpatent documents. The details of CMOS in one transferred layer and theorthogonal connect strip methodology may be found as illustrated in atleast FIGS. 30-27, 73-80, and 94 and related specification sections ofU.S. Pat. No. 8,273,610. As discussed above and herein this document andreferenced patent documents, annealing of dopants or annealing ofdamage, such as from the dopant application such as ion-implantation, orfrom etch processes during the formation of the transferred layertransistor and device structures, may be accomplished by opticalannealing. Donor wafer device structures 2750 may include transistorsand/or semiconductor regions wherein the dopant concentration of theregions in the horizontal plane, such as shown as exemplary dopant plane2749, may have regions that differ substantially in dopantconcentration, for example, 10× greater, and/or may have a differentdopant type, such as, for example p-type or n-type dopant. Additionally,the annealing of deposited dielectrics and etch damage, for example,oxide depositions and silicon etches utilized in the transferred layerisolation processing, for example, STI (Shallow Trench Isolation)processing or strained source and drain processing, may be accomplishedby optical annealing. An optical step may be performed to densify and/orremove defects from gate dielectric, anneal defects and activate dopantssuch as LDD and S/D implants, densify ILDs, form DSS junctions (DopantSegregated Schottky such as NiSi₂), and/or form contact and S/Dsilicides (not shown). The optical anneal may be performed at eachsub-step as desired, or may be done at prior to the HKMG deposition(such as after the dummy gate but before the HKMG formation), or variouscombinations. Second device layer metal interconnect 2761 may includeelectrically conductive materials such as copper, aluminum, conductiveforms of carbon, and tungsten. Donor wafer device structures 2750 mayutilize second device layer metal interconnect 2761 and thru layer vias(TLVs) 2760 to electrically couple (connection paths) the donor waferdevice structures 2750 to the acceptor wafer metal connect pads orstrips 2780, and thus couple donor wafer device structures (the secondlayer transistors) with acceptor wafer device structures (first layertransistors). Thermal TLVs 2762 may be constructed of thermallyconductive but not electrically conductive materials, for example, DLC(Diamond Like Carbon), and may connect donor wafer device structures2750 thermally to shield/heat sink layer 2788. TLVs 2760 may beconstructed out of electrically and thermally conductive materials, suchas Tungsten, Copper, or aluminum, and may provide a thermal andelectrical connection path from donor wafer device structures 2750 toshield/heat sink layer 2788, which may be a ground or Vdd plane in thedesign/layout. TLVs 2760 and thermal TLVs 2762 may be also constructedin the device scribelanes (pre-designed in base layers or potentialdicelines) to provide thermal conduction to the heat sink, and may besawed/diced off when the wafer is diced for packaging. Shield/heat sinklayer 2788 may be configured to act as an emf (electro-motive force)shield to prevent direct layer to layer cross-talk between transistorsin the donor wafer layer and transistors in the acceptor wafer. Inaddition to static ground or Vdd biasing, shield/heat sink layer 2788may be actively biased with an anti-interference signal from circuitryresiding on, for example, a layer of the 3D-IC or off chip. TLVs 2760may be formed through the transferred layers 2702. As the transferredlayers 2702 may be thin, on the order of about 200 nm or less inthickness, the TLVs may be easily manufactured as a typical metal tometal via may be, and said TLV may have state of the art diameters suchas nanometers or tens to a few hundreds of nanometers, such as, forexample about 150 nm or about 100 nm or about 50 nm. The thinner thetransferred layers 2702, the smaller the thru layer via diameterobtainable, which may result from maintaining manufacturable via aspectratios. Thus, the transferred layers 2702 (and hence, TLVs 2760) may be,for example, less than about 2 microns thick, less than about 1 micronthick, less than about 0.4 microns thick, less than about 200 nm thick,less than about 150 nm thick, less than about 100 nm thick, less thanabout 50 nm thick, less than about 20 nm thick, or less than about 5 nmthick. The thickness of the layer or layers transferred according tosome embodiments of the invention may be designed as such to match andenable the most suitable obtainable lithographic resolution (and enablethe use of conventional state of the art lithographic tools), such as,for example, less than about 10 nm, 14 nm, 22 nm or 28 nm linewidthresolution and alignment capability, such as, for example, less thanabout 5 nm, 10 nm, 20 nm, or 40 nm alignment accuracy/precision/error,of the manufacturing process employed to create the thru layer vias orany other structures on the transferred layer or layers. The above TLVdimensions and alignment capability and transferred layer thicknessesmay be also applied to any of the discussed TLVs or transferred layersdescribed elsewhere herein. Transferred layers 2702 may be considered tobe overlying the metal layer or layers of acceptor wafer 2710. Alignmentmarks in acceptor wafer 2710 and/or in transferred layers 2702 may beutilized to enable reliable contact to transistors and circuitry intransferred layers 2702 and donor wafer device structures 2750 andelectrically couple them to the transistors and circuitry in theacceptor wafer 2710. Transferred layer or layers may have regions of STIor other transistor elements within it or on it when transferred, butwould then use alignment and connection schemes for layer transfer ofpatterned layers as described in incorporated patent references. Thedonor wafer 2700 may now also be processed, such as smoothing andannealing, and reused for additional layer transfers. The transferredlayers 2702 and other additional regions created in the transferredlayers during transistor processing are thin and small, having smallvolumes on the order of 2×10⁻¹⁶ cm³ (2×10⁵ nm³ for a 100 nm by 100 nm×20nm thick device). As a result, the amount of energy to manufacture withknown in the art transistor and device formation processing, forexample, annealing of ion-cut created defects or activation of dopantsand annealing of doping or etching damages, is very small and may leadto only a small amount of shield layer or layers or regions or none toeffectively shield the underlying interconnect metallization anddielectrics from the manufacturing processing generated heat. The energymay be supplied by, for example, pulsed and short wavelength opticalannealing techniques described herein and incorporated references, andmay include the use of optical absorbers and reflectors andoptical/thermal shielding and heat spreaders, some of which aredescribed herein and incorporated references. The optical anneal may beperformed at each sub-step as desired, or may be done at prior to theHKMG deposition (such as after the dummy gate but before the HKMGformation), or various combinations. Moreover, multiple pulses of thelaser may be utilized to improve the anneal, activation, and yield ofthe process.

As illustrated in FIG. 27F, a thermal conduction path may be constructedfrom the devices in the upper layer, the transferred donor layer andformed transistors, to the acceptor wafer substrate and associated heatsink. The thermal conduction path from the donor wafer device structures2750 to the acceptor wafer heat sink 2797 may include second devicelayer metal interconnect 2761, TLVs 2760, shield path connect 2785,shield path via 2783, metal connect pads or strips 2780, first(acceptor) layer metal interconnect 2791, acceptor wafer transistors anddevices 2793, and acceptor substrate 2795. The elements of the thermalconduction path may include materials that have a thermal conductivitygreater than 10 W/m-K, for example, copper (about 400 W/m-K), aluminum(about 237 W/m-K), and Tungsten (about 173 W/m-K), and may includematerial with thermal conductivity lower than 10 W/m-K but have a highheat transfer capacity due to the wide area available for heat transferand thickness of the structure (Fourier's Law), such as, for example,acceptor substrate 2795. The elements of the thermal conduction path mayinclude materials that are thermally conductive but may not besubstantially electrically conductive, for example, Plasma EnhancedChemical Vapor Deposited Diamond Like Carbon-PECVD DLC (about 1000W/m-K), and Chemical Vapor Deposited (CVD) graphene (about 5000 W/m-K).The acceptor wafer interconnects may be substantially surrounded by BEOLdielectric 2796. In general, within the active device or devices (thatare generating the heat that is desired to be conducted away thru atleast the thermal conduction path), it would be advantageous to have aneffective conduction path to reduce the overall space and area that adesigner would allocate for heat transfer out of the active circuitryspace and area. A designer may select to use only materials with a highthermal conductivity (such as greater than 10 W/m-K), much higher forexample than that for monocrystalline silicon, for the desired thermalconduction path. However, there may need to be lower than desiredthermal conductivity materials in the heat conduction path due torequirements such as, for example, the mechanical strength of a thicksilicon substrate, or another heat spreader material in the stack. Thearea and volume allocated to that structure, such as the siliconsubstrate, is far larger than the active circuit area and volume.Accordingly, since a copper wire of 1 um² profile is about the same as a286 um² profile of a column of silicon, and the thermal conduction pathmay include both a copper wire/TLV/via and the bulk silicon substrate, aproper design may take into account and strive to align the differentelements of the conductive path to achieve effective heat transfer andremoval, for example, may attempt to provide about 286 times the siliconsubstrate area for each Cu thermal via utilized in the thermalconduction path. The heat removal apparatus, which may include acceptorwafer heat sink 2797, may include an external surface from which heattransfer may take place by methods such as air cooling, liquid cooling,or attachment to another heat sink or heat spreader structure.

Formation of CMOS in one transferred layer and the orthogonal connectstrip methodology may be found as illustrated in at least FIGS. 30-33,73-80, and 94 and related specification sections of U.S. Pat. No.8,273,610, and may be applied to at least the FIG. 27 formationtechniques. Transferred layer or layers may have regions of STI or othertransistor elements within it or on it when transferred, but would thenuse alignment and connection schemes for layer transfer of patternedlayers as described in incorporated patent references.

A planar fully depleted n-channel Recessed Channel Array Transistor(FD-RCAT) with an integrated shield/heat sink layer suitable for amonolithic 3D IC may be constructed as follows. The FD-RCAT may providean improved source and drain contact resistance, thereby allowing forlower channel doping (such as undoped), and the recessed channel mayprovide for more flexibility in the engineering of channel lengths andtransistor characteristics, and increased immunity from processvariations. The buried doped layer and channel dopant shaping, even toan un-doped channel, may allow for efficient adaptive and dynamic bodybiasing to control the transistor threshold and threshold variations, aswell as provide for a fully depleted or deeply depleted transistorchannel. Furthermore, the recessed gate allows for an FD transistor butwith thicker silicon for improved lateral heat conduction. Moreover, aheat spreading, heat conducting and/or optically reflecting materiallayer or layers may be incorporated between the sensitive metalinterconnect layers and the layer or regions being optically irradiatedand annealed to repair defects in the crystalline 3D-IC layers andregions and to activate semiconductor dopants in the crystalline layersor regions of a 3D-IC without harm to the sensitive metal interconnectand associated dielectrics. FIG. 28A-G illustrates an exemplaryn-channel FD-RCAT which may be constructed in a 3D stacked layer usingprocedures outlined below and in U.S. Pat. Nos. 8,273,610, 9,099,526,9,219,005, 8,557,632 and 8,581,349. The contents of the foregoingapplications are incorporated herein by reference.

As illustrated in FIG. 28A, a P− substrate donor wafer 2800 may beprocessed to include wafer sized layers of N+ doping 2802, P− doping2806, channel 2803 and P+ doping 2804 across the wafer. The N+ dopedlayer 2802, P− doped layer 2806, channel layer 2803 and P+ doped layer2804 may be formed by ion implantation and thermal anneal. P− substratedonor wafer 2800 may include a crystalline material, for example,mono-crystalline (single crystal) silicon. P− doped layer 2806 andchannel layer 2803 may have additional ion implantation and annealprocessing to provide a different dopant level than P− substrate donorwafer 2800. P− substrate donor wafer 2800 may be very lightly doped(less than 1e15 atoms/cm³) or nominally un-doped (less than 1e14atoms/cm³). P− doped layer 2806, channel layer 2803, and P+ doped layer2804 may have graded or various layers doping to mitigate transistorperformance issues, such as, for example, short channel effects, afterthe FD-RCAT is formed, and to provide effective body biasing, whetheradaptive or dynamic. The layer stack may alternatively be formed bysuccessive epitaxially deposited doped silicon layers of N+ doped layer2802, P− doped layer 2806, channel layer 2803 and P+ doped layer 2804,or by a combination of epitaxy and implantation, or by layer transfer.Annealing of implants and doping may include, for example,conductive/inductive thermal, optical annealing techniques or types ofRapid Thermal Anneal (RTA or spike). The N+ doped layer 2802 may have adoping concentration that may be more than 10× the doping concentrationof P− doped layer 2806 and/or channel layer 2803. The P+ doped layer2804 may have a doping concentration that may be more than 10× thedoping concentration of P− doped layer 2806 and/or channel layer 2803.The P− doped layer 2806 may have a doping concentration that may be morethan 10× the doping concentration of channel layer 2803. Channel layer2803 may have a thickness and/or doping that may allow fully-depletedchannel operation when the FD-RCAT transistor is substantiallycompletely formed, such as, for example, less than 5 nm, less than 10nm, or less than 20 nm.

As illustrated in FIG. 28B, the top surface of the P− substrate donorwafer 2800 layer stack may be prepared for oxide wafer bonding with adeposition of an oxide or by thermal oxidation of P+ doped layer 2804 toform oxide layer 2880. A layer transfer demarcation plane (shown asdashed line) 2899 may be formed by hydrogen implantation or othermethods as described in the incorporated references. The P− substratedonor wafer 2800 and acceptor wafer 2810 may be prepared for waferbonding as previously described and low temperature (less thanapproximately 400° C.) bonded. Acceptor wafer 2810, as described in theincorporated references, may include, for example, transistors,circuitry, and metal, such as, for example, aluminum or copper,interconnect wiring, a metal shield/heat sink layer, and thru layer viametal interconnect strips or pads. Acceptor wafer 2810 may besubstantially comprised of a crystalline material, for examplemono-crystalline silicon or germanium, or may be an engineeredsubstrate/wafer such as, for example, an SOI (Silicon on Insulator)wafer or GeOI (Germanium on Insulator) substrate. SOI Acceptor wafer2810 may include transistors such as, for example, MOSFETS, FinFets,FD-RCATs, BJTs, HEMTs, and/or HBTs. The portion of the N+ doped layer2802 and the P− substrate donor wafer 2800 that may be above (when thelayer stack is flipped over and bonded to the acceptor wafer) the layertransfer demarcation plane 2899 may be removed by cleaving or other lowtemperature processes as described in the incorporated references, suchas, for example, ion-cut or other layer transfer methods Damage/defectsto crystalline structure of N+ doped layer 2802, P− doped layer 2806,channel layer 2803 and P+ doped layer 2804 may be annealed by some ofthe annealing methods described, for example the short wavelength pulsedlaser techniques, wherein the N+ doped layer 2802, P− doped layer 2806,channel layer 2803 and P+ doped layer 2804 or portions of them may beheated to defect annealing temperatures, but the layer transferdemarcation plane 2899 may be kept below the temperate for cleavingand/or significant hydrogen diffusion. The optical energy may bedeposited in the upper layer of the stack, for example in P+ doped layer2804, and annealing of the other layer may take place via heatdiffusion. Dopants in at least a portion of N+ doped layer 2802, P−doped layer 2806, channel layer 2803 and P+ doped layer 2804 may also beelectrically activated by the anneal.

As illustrated in FIG. 28C, oxide layer 2880, P+ doped layer 2804,channel layer 2803, P− doped layer 2806, and remaining N+ layer 2822have been layer transferred to acceptor wafer 2810. The top surface ofN+ layer 2822 may be chemically or mechanically polished. Thru theprocessing, the wafer sized layers such as N+ layer 2822 P+ doped layer2804, channel layer 2803, and P− doped layer 2806, could be thinned fromits original total thickness, and their/its final total thickness couldbe in the range of about 0.01 um to about 50 um, for example, 10 nm, 100nm, 200 nm, 0.4 um, 1 um, 2 um or 5 um. Acceptor wafer 2810 may includeone or more (two are shown in this example) shield/heat sink layers2888, which may include materials such as, for example, Aluminum,Tungsten (a refractory metal), Copper, silicon or cobalt basedsilicides, or forms of carbon such as carbon nanotubes, and may belayered itself as described in FIG. 50 of incorporated patent referenceU.S. Pat. No. 9,385,058. Each shield/heat sink layer 2888 may have athickness range of about 50 nm to about 1 mm, for example, 50 nm, 100nm, 200 nm, 300 nm, 500 nm, 0.1 um, 1 um, 2 um, and 10 um. Shield/heatsink layer 2888 may include isolation openings 2887, and alignment markopenings (not shown), which may be utilized for short wavelengthalignment of top layer (donor) processing to the acceptor waferalignment marks (not shown). Shield/heat sink layer 2888 may include oneor more shield path connect 2885 and shield path via 2883. Shield pathvia 2883 may thermally and/or electrically couple and connect shieldpath connect 2885 to acceptor wafer 2810 interconnect metallizationlayers such as, for example, acceptor metal interconnect 2881 (shown).Shield path connect 2885 may also thermally and/or electrically coupleand connect each shield/heat sink layer 2888 to the other and toacceptor wafer 2810 interconnect metallization layers such as, forexample, acceptor metal interconnect 2881, thereby creating a heatconduction path from the shield/heat sink layer 2888 to the acceptorsubstrate 2895, and a heat sink (shown in FIG. 28G). Isolation openings2887 may include dielectric materials, similar to those of BEOLisolation 2896. Acceptor wafer 2810 may include first (acceptor) layermetal interconnect 2891, acceptor wafer transistors and devices 2893,and acceptor substrate 2895. Various topside defect anneals may beutilized. For this illustration, an optical beam such as the laserannealing previously described is used. Optical anneal beams may beoptimized to focus light absorption and heat generation within or at thesurface of N+ layer 2822 and provide surface smoothing and/or defectannealing (defects may be from the cleave and/or the ion-cutimplantation) with exemplary smoothing/annealing ray 2866. The laserassisted smoothing/annealing with the absorbed heat generated byexemplary smoothing/annealing ray 2866 may also include a pre-heat ofthe bonded stack to, for example, about 100° C. to about 400° C., and/ora rapid thermal spike to temperatures above about 200° C. to about 600°C. Additionally, absorber layers or regions, for example, includingamorphous carbon, amorphous silicon, and phase changing materials (seeU.S. Pat. Nos. 6,635,588 and 6,479,821 to Hawryluk et al. for example),may be utilized to increase the efficiency of the optical energy capturein conversion to heat for the desired annealing or activation processes.Reflected ray 2863 may be reflected and/or absorbed by shield/heat sinklayer 2888 regions thus blocking the optical absorption of ray blockedmetal interconnect 2881. Annealing of dopants or annealing of damage,such as from the H cleave implant damage, may be also accomplished by aset of rays such as repair ray 2865. Heat generated by absorbed photonsfrom, for example, smoothing/annealing ray 2866, reflected ray 2863,and/or repair ray 2865 may also be absorbed by shield/heat sink layer2888 regions and dissipated laterally and may keep the temperature ofunderlying metal layers, such as metal interconnect 2881, and othermetal layers below it, cooler and prevent damage. Shield/heat sink layer2888 and associated dielectrics may laterally spread and conduct theheat generated by the topside defect anneal, and in conjunction with thedielectric materials (low heat conductivity) above and below shield/heatsink layer 2888, keep the interconnect metals and low-k dielectrics ofthe acceptor wafer interconnect layers cooler than a damage temperature,such as, for example, 400° C. A second layer of shield/heat sink layer2888 may be constructed (shown) with a low heat conductive materialsandwiched between the two heat sink layers, such as silicon oxide orcarbon doped ‘low-k’ silicon oxides, for improved thermal protection ofthe acceptor wafer interconnect layers, metal and dielectrics.Shield/heat sink layer 2888 may act as a heat spreader. Electricallyconductive materials may be used for the two layers of shield/heat sinklayer 2888 and thus may provide, for example, a Vss and a Vdd planeand/or grid that may be connected to the donor layer transistors above,as well may be connected to the acceptor wafer transistors below. Noiseon the power grids, such as the Vss and Vdd plane power conductinglines/wires, may be mitigated by attaching/connecting decouplingcapacitors onto the power conducting lines of the grids. The decouplingcaps, which may be within the second layer (donor, for example, donorwafer device structures) or first layer (acceptor, for example acceptorwafer transistors and devices 2893), may include, for example, trenchcapacitors such as described by Pei, C., et al., “A novel, low-cost deeptrench decoupling capacitor for high-performance, low-power bulk CMOSapplications,” ICSICT (9^(th) International Conference on Solid-Stateand Integrated-Circuit Technology) 2008, October 2008, pp. 1146-1149, ofIBM. The decoupling capacitors may include, for example, planarcapacitors, such as poly to substrate or poly to poly, or MiM capacitors(Metal-Insulator-Metal). Shield/heat sink layer 2888 may includematerials with a high thermal conductivity greater than 10 W/m-K, forexample, copper (about 400 W/m-K), aluminum (about 237 W/m-K), Tungsten(about 173 W/m-K), Plasma Enhanced Chemical Vapor Deposited Diamond LikeCarbon-PECVD DLC (about 1000 W/m-K), and Chemical Vapor Deposited (CVD)graphene (about 5000 W/m-K). Shield/heat sink layer 2888 may besandwiched and/or substantially enclosed by materials with a low thermalconductivity (less than 10 W/m-K), for example, silicon dioxide (about1.4 W/m-K). The sandwiching of high and low thermal conductivitymaterials in layers, such as shield/heat sink layer 2888 and under &overlying dielectric layers, spreads the localized heat/light energy ofthe topside anneal laterally and protect the underlying layers ofinterconnect metallization & dielectrics, such as in the acceptor wafer,from harmful temperatures or damage. When there may be more than oneshield/heat sink layer 2888 in the device, the heat conducting layerclosest to the second crystalline layer or oxide layer 2880 may beconstructed with a different material, for example a high melting pointmaterial, for example a refractory metal such as tungsten, than theother heat conducting layer or layers, which may be constructed with,for example, a lower melting point material, for example, such asaluminum or copper. Now transistors may be formed with low effectivetemperature (less than approximately 400° C. exposure to the acceptorwafer 2810 sensitive layers, such as interconnect and device layers)processing, and may be aligned to the acceptor wafer alignment marks(not shown) as described in the incorporated references. This mayinclude further optical defect annealing or dopant activation steps. Thedonor wafer 2800 may now also be processed, such as smoothing andannealing, and reused for additional layer transfers. The insulatorlayer, such as deposited bonding oxides (for example oxide layer 2880)and/or before bonding preparation existing oxides (for example the BEOLisolation 2896 on top of the topmost metal layer of shield/heat sinklayer 2888), between the donor wafer transferred monocrystalline layerand the acceptor wafer topmost metal layer, may include thicknesses ofless than 1 um, less than 500 nm, less than 400 nm, less than 300 nm,less than 200 nm, or less than 100 nm.

As illustrated in FIG. 28D, transistor isolation regions 2805 may beformed by mask defining and plasma/RIE etching remaining N+ layer 2822,P− doped layer 2806, channel layer 2803, and P+ doped layer 2804substantially to the top of oxide layer 2880 (not shown), substantiallyinto oxide layer 2880, or into a portion of the upper oxide layer ofacceptor wafer 2810 (not shown). Additionally, a portion of thetransistor isolation regions 2805 may be etched (separate step)substantially to P+ doped layer 2804, thus allowing multiple transistorregions to be connected by the same P+ doped region 2824. Alow-temperature gap fill oxide may be deposited and chemicallymechanically polished, the oxide remaining in isolation regions 2805. Anoptical step, such as illustrated by exemplary STI ray 2867, may beperformed to anneal etch damage and densify the STI oxide in isolationregions 2805. The recessed channel 2886 may be mask defined and etchedthru remaining N+ doped layer 2822, P− doped layer 2806 and partiallyinto channel layer 2803. The recessed channel surfaces and edges may besmoothed by processes, such as, for example, wet chemical, plasma/RIEetching, low temperature hydrogen plasma, or low temperature oxidationand strip techniques, or optical annealing (such as illustrated byexemplary channel smoothing ray 2868, which may induce local short termhigh temperatures) as described herein, to mitigate high field effects(see Kim, J. Y., et al., “The breakthrough in data retention time ofDRAM using Recess-Channel-Array Transistor (RCAT) for 88 nm feature sizeand beyond,” 2003 Symposium on VLSI Technology Digest of TechnicalPapers, pp. 11-12, 10-12 Jun. 2003, for CDE (chemical dry etch)smoothing). The low temperature smoothing process may employ, forexample, a plasma produced in a TEL (Tokyo Electron Labs) SPA (SlotPlane Antenna) machine. Thus N+ source and drain regions 2832, P−regions 2826, and channel region 2823 may be formed, which maysubstantially form the transistor body. The doping concentration of N+source and drain regions 2832 may be more than 10× the concentration ofchannel region 2823. The doping concentration of the N− channel region2823 may include gradients of concentration or layers of differingdoping concentrations. The doping concentration of N+ source and drainregions 2832 may be more than 10× the concentration of P− regions 2826.The etch formation of recessed channel 2886 may define the transistorchannel length. The shape of the recessed etch may be rectangular asshown, or may be spherical (generally from wet etching, sometimes calledan S-RCAT: spherical RCAT), or a variety of other shapes due to etchingmethods and shaping from smoothing processes, and may help control forthe channel electric field uniformity. The thickness of channel region2823 in the region below recessed channel 2886 may be of a thicknessthat allows fully-depleted channel operation. The thickness of channelregion 2823 in the region below N+ source and drain regions 2832 may beof a thickness that allows fully-depleted transistor operation. Anyadditional doping, such as ion-implanted halo implants, may be activatedand annealed with optical annealing, such as illustrated by exemplaryimplant ray 2869, as described herein. The optical anneal, such asexemplary STI ray 2867, exemplary channel smoothing ray 2868, and/orexemplary implant ray 2869 may be performed at separate times andprocessing parameters (such as laser energy, frequency, etc.) or may bedone in combination or as one optical anneal.

As illustrated in FIG. 28E, a gate dielectric 2807 may be formed and agate metal material may be deposited. The gate dielectric 2807 may be anatomic layer deposited (ALD) gate dielectric that may be paired with awork function specific gate metal in the industry standard high k metalgate process schemes described in the incorporated references.Alternatively, the gate dielectric 2807 may be formed with a lowtemperature processes including, for example, LPCVD SiO₂ oxidedeposition (see Ahn, J., et al., “High-quality MOSFET's with ultrathinLPCVD gate SiO2,” IEEE Electron Device Lett., vol. 13, no. 4, pp.186-188, April 1992) or low temperature microwave plasma oxidation ofthe silicon surfaces (see Kim, J. Y., et al., “The excellent scalabilityof the RCAT (recess-channel-array-transistor) technology for sub-70 nmDRAM feature size and beyond,” 2005 IEEE VLSI-TSA InternationalSymposium, pp. 33-28, 25-27 Apr. 2005) and a gate material with properwork function and less than approximately 400° C. deposition temperaturesuch as, for example, tungsten or aluminum may be deposited. An opticalstep, such as represented by exemplary gox ray 2821, may be performed todensify and/or remove defects from gate dielectric 2807. The gatematerial may be chemically mechanically polished, and the gate areadefined by masking and etching, thus forming the gate electrode 2808.The shape of gate electrode 2808 is illustrative, the gate electrode mayalso overlap a portion of N+ source and drain regions 2832. An opticalstep, such as represented by exemplary gox ray 2821, may be performed toanneal defects and activate dopants such as LDD and S/D implants,densify an ILD thick oxide 2809, form DSS junctions (Dopant SegregatedSchottky such as NiSi₂), and/or form contact and S/D silicides (notshown). The optical anneal may be performed at each sub-step as desired,or may be done at prior to the HKMG deposition (such as after the dummygate but before the HKMG formation), or various combinations. Moreover,multiple pulses of the laser may be utilized to improve the anneal,activation, and yield of the process.

As illustrated in FIG. 28F, a low temperature thick oxide 2809 may bedeposited and planarized. Source, gate, and drain contacts, P+ dopedregion contact (not shown) openings may be masked and etched preparingthe transistors to be connected via metallization. P+ doped regioncontact may be constructed thru isolation regions 2805, suitably whenthe isolation regions 2805 is formed to a shared P+ doped region 2824.Thus gate contact 2811 connects to gate electrode 2808, and source &drain contacts 2840 connect to N+ source and drain regions 2832. Anoptical step, such as illustrated by exemplary STI ray 2831, may beperformed to anneal contact etch damage and densify the thick oxide2809.

As illustrated in FIG. 28G, thru layer vias (TLVs) 2860 may be formed byetching thick oxide 2809, gate dielectric 2807, isolation regions 2805,oxide layer 2880, into a portion of the upper oxide layer BEOL isolation2896 of acceptor wafer 2810 BEOL, and filling with an electrically andthermally conducting material or an electrically non-conducting butthermally conducting material. Second device layer metal interconnect2861 may be formed by conventional processing. TLVs 2860 may beconstructed of thermally conductive but not electrically conductivematerials, for example, DLC (Diamond Like Carbon), and may connect theFD-RCAT transistor device and other devices on the top (second)crystalline layer thermally to shield/heat sink layer 2888. TLVs 2860may be constructed out of electrically and thermally conductivematerials, such as Tungsten, Copper, or aluminum, and may provide athermal and electrical connection path from the FD-RCAT transistordevice and other devices on the top (second) crystalline layer toshield/heat sink layer 2888, which may be a ground or Vdd plane in thedesign/layout. TLVs 2860 may be also constructed in the devicescribelanes (pre-designed in base layers or potential dicelines) toprovide thermal conduction to the heat sink, and may be sawed/diced offwhen the wafer is diced for packaging not shown). Shield/heat sink layer2888 may be configured to act (or adapted to act) as an emf(electro-motive force) shield to prevent direct layer to layercross-talk between transistors in the donor wafer layer and transistorsin the acceptor wafer. In addition to static ground or Vdd biasing,shield/heat sink layer 2888 may be actively biased with ananti-interference signal from circuitry residing on, for example, alayer of the 3D-IC or off chip. A thermal conduction path may beconstructed from the devices in the upper layer, the transferred donorlayer and formed transistors, to the acceptor wafer substrate andassociated heat sink. The thermal conduction path from the FD-RCATtransistor device and other devices on the top (second) crystallinelayer, for example, N+ source and drain regions 2832, to the acceptorwafer heat sink 2897 may include source & drain contacts 2840, seconddevice layer metal interconnect 2861, TLV 2860, shield path connect 2885(shown as twice), shield path via 2883 (shown as twice), metalinterconnect 2881, first (acceptor) layer metal interconnect 2891,acceptor wafer transistors and devices 2893, and acceptor substrate2895. The elements of the thermal conduction path may include materialsthat have a thermal conductivity greater than 10 W/m-K, for example,copper (about 400 W/m-K), aluminum (about 237 W/m-K), and Tungsten(about 173 W/m-K). The heat removal apparatus, which may includeacceptor wafer heat sink 2897, may include an external surface fromwhich heat transfer may take place by methods such as air cooling,liquid cooling, or attachment to another heat sink or heat spreaderstructure.

It should be noted that one of the design requirements for a monolithic3D IC design may be that substantially all of the stacked layers and thebase or substrate would have their respective dice lines (may be calledscribelines) aligned. As the base wafer or substrate is processed andmultiple circuits may be constructed on semiconductor layers thatoverlay each other, the overall device may be designed wherein eachoverlaying layer would have its respective dice lines overlying the dicelines of the layer underneath, thus at the end of processing the entirelayer stacked wafer/substrate could be diced in a dicing step. There maybe test structures in the streets between dice lines, which overall maybe called scribelanes or dicelanes. These scribelanes or dicelanes maybe 10 um wide, 20 um wide, 50 um wide 100 um wide, or greater than 100um wide depending on design choice and die singulation processcapability. The scribelanes or dicelanes may include guard-ringstructures and/or other die border structures. In a monolithic 3D designeach layer test structure could be connected through each of theoverlying layers and then to the top surface to allow access to these‘buried’ test structure before dicing the wafer. Accordingly the designmay include these vertical connections and may offset the layer teststructures to enable such connection. In many cases the die borderscomprise a protection structure, such as, for example, a guard-ringstructure, die seal structure, ESD structure, and others elements.Accordingly in a monolithic 3D device these structures, such as guardrings, would be designed to overlay each other and may be aligned toeach other during the course of processing. The die edges may be sealedby a process and structure such as, for example, described in relationto FIG. 183C of incorporated U.S. Pat. No. 8,273,610, and may includeaspects as described in relation to FIGS. 183A and 183B of samereference. One skilled in the art would recognize that the die seal canbe passive or electrically active. On each 3D stack layer, or stratum,the electronic circuits within one die, that may be circumscribed by adicelane, may not be connected to the electronic circuits of a seconddie on that same wafer, that second die also may be circumscribed by adicelane. Further, the dicelane/scribelane of one stratum in the 3Dstack may be aligned to the dicelane/scribelane of another stratum inthe 3D stack, thus providing a direct die singulation vector for the 3Dstack of stratums/layers.

Furthermore, some or all of the layers utilized as shield/heat sinklayer 2888, which may include shapes of material such as the strips orfingers as illustrated in FIG. 27B-1 , may be driven by a portion of thesecond layer transistors and circuits (within the transferred donorwafer layer or layers) or the acceptor wafer transistors and circuits,to provide a programmable back-bias to at least a portion of the secondlayer transistors. The programmable back bias may utilize a circuit todo so, for example, such as shown in FIG. 17B of U.S. Pat. No.8,273,610, the contents incorporated herein by reference; wherein the‘Primary’ layer may be the second layer of transistors for which theback-bias is being provided, the ‘Foundation’ layer could be either thesecond layer transistors (donor) or first layer transistors (acceptor),and the routing metal lines connections 1723 and 1724 may includeportions of the shield/heat sink layer 2888 layer or layers. Moreover,some or all of the layers utilized as shield/heat sink layer 2888, whichmay include strips or fingers as illustrated in FIG. 27B-1 , may bedriven by a portion of the second layer transistors and circuits (withinthe transferred donor wafer layer or layers) or the acceptor wafertransistors and circuits to provide a programmable power supply to atleast a portion of the second layer transistors. The programmable powersupply may utilize a circuit to do so, for example, such as shown inFIG. 17C of U.S. Pat. No. 8,273,610, the contents incorporated herein byreference; wherein the ‘Primary’ layer may be the second layer oftransistors for which the programmable power supplies are being providedto, the ‘Foundation’ layer could be either the second layer transistors(donor) or first layer transistors (acceptor), and the routing metalline connections from Vout to the various second layer transistors mayinclude portions of the shield/heat sink layer 2888 layer or layers. TheVsupply on line 17C12 and the control signals on control line 17C16 maybe controlled by and/or generated in the second layer transistors (forexample donor wafer device structures such as the FD-RCATs formed asdescribed in relation to FIG. 28 ) or first layer transistors (acceptor,for example acceptor wafer transistors and devices 2893), or off chipcircuits. Furthermore, some or all of the layers utilized as shield/heatsink layer 2888, which may include strips or fingers as illustrated inFIG. 27B-1 or other shapes such as those in FIG. 27B, may be utilized todistribute independent power supplies to various portions of the secondlayer transistors (for example donor wafer device structures such as theFD-RCATs formed as described in relation to FIG. 28 of incorporatedpatent reference U.S. Pat. No. 9,385,058) or first layer transistors(acceptor, for example acceptor wafer transistors and devices 2893 ofincorporated patent reference U.S. Pat. No. 9,385,058) and circuits; forexample, one power supply and/or voltage may be routed to the sequentiallogic circuits of the second layer and a different power supply and/orvoltage routed to the combinatorial logic circuits of the second layer.Moreover, the power distribution circuits/grid may be designed so thatVdd may have a different value for each stack layer. Patterning ofshield/heat sink layer 2888 or layers can impact their heat-shieldingcapacity. This impact may be mitigated, for example, by enhancing thetop shield/heat sink layer 2888 areal density, creating more of thesecondary shield/heat sink layers 2888, or attending to special CADrules regarding their metal density, similar to CAD rules that arerequired to accommodate Chemical-Mechanical Planarization (CMP). Theseconstraints would be integrated into a design and layout EDA tool

TLVs 2860 may be formed through the transferred layers. As thetransferred layers may be thin, on the order of about 200 nm or less inthickness, the TLVs may be easily manufactured as a typical metal tometal via may be, and said TLV may have state of the art diameters suchas nanometers or tens to a few hundreds of nanometers, such as, forexample about 150 nm or about 100 nm or about 50 nm. The thinner thetransferred layers, the smaller the thru layer via diameter obtainable,which may result from maintaining manufacturable via aspect ratios. Thethickness of the layer or layers transferred according to someembodiments of the invention may be designed as such to match and enablethe most suitable obtainable lithographic resolution (and enable the useof conventional state of the art lithographic tools), such as, forexample, less than about 10 nm, 14 nm, 22 nm or 28 nm linewidthresolution and alignment capability, such as, for example, less thanabout 5 nm, 10 nm, 20 nm, or 40 nm alignment accuracy/precision/error,of the manufacturing process employed to create the thru layer vias orany other structures on the transferred layer or layers.

As illustrated in FIG. 28G-1 , at least one conductive bond pad 2864 forinterfacing electrically (and may thermally) to external devices may beformed on top of the completed device and may include at least one metallayer of second device layer metal interconnect 2861. Bond pad 2864 mayoverlay second device layer metal interconnect 2861 or a portion of(some of the metal and insulator layers of) second device layer metalinterconnect 2861. Bond pad 2864 may be directly aligned to the acceptorwafer alignment marks (not shown) and the I/O driver circuitry may beformed by the second layer (donor) transistors, for example, donor waferdevice structures such as the FD-RCATs formed as described in relationto FIG. 28 . Bond pad 2864 may be connected to the second layertransistors thru the second device layer metal interconnect 2861 whichmay include vias 2862. The I/O driver circuitry may be formed bytransistors from the acceptor wafer transistors and devices 2893, orfrom transistors in other strata if the 3DIC device has more than twolayers of transistors. I/O pad control metal segment 2867 may be formeddirectly underneath bond pad 2864 and may influence the noise and ESD(Electro Static Discharge) characteristics of bond pad 2864. The emfinfluence of I/O pad control metal segment 2867 may be controlled bycircuitry formed from a portion of the second layer transistors. I/O padcontrol metal segment 2867 may be formed with second device layer metalinterconnect 2861.

Formation of CMOS in one transferred layer and the orthogonal connectstrip methodology may be found as illustrated in at least FIGS. 30-33,73-80, and 94 and related specification sections of U.S. Pat. No.8,273,610, and may be applied to at least the FIG. 28 formationtechniques herein. Transferred layer or layers may have regions of STIor other transistor elements within it or on it when transferred, butwould then use alignment and connection schemes for layer transfer ofpatterned layers as described in incorporated patent references.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 28A through 28G are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations are possible such as, for example, a p-channel FD-RCAT may beformed with changing the types of dopings appropriately. Moreover, theP− substrate donor wafer 2800 may be n type or un-doped. Further, P−doped channel layer 2803 may include multiple layers of different dopingconcentrations and gradients to fine tune the eventual FD-RCAT channelfor electrical performance and reliability characteristics, such as, forexample, off-state leakage current and on-state current. Furthermore,isolation regions 2805 may be formed by a hard mask defined processflow, wherein a hard mask stack, such as, for example, silicon oxide andsilicon nitride layers, or silicon oxide and amorphous carbon layers,may be utilized. Moreover, CMOS FD-RCATs may be constructed withn-JLRCATs in a first mono-crystalline silicon layer and p-JLRCATs in asecond mono-crystalline layer, which may include different crystallineorientations of the mono-crystalline silicon layers, such as forexample, <100>, <111> or <551>, and may include different contactsilicides for optimum contact resistance to p or n type source, drains,and gates. Furthermore, P+ doped regions 2824 may be utilized for adouble gate structure for the FD-RCAT and may utilize techniquesdescribed in the incorporated references. Further, efficient heatremoval and transistor body biasing may be accomplished on a FD-RCAT byadding an appropriately doped buried layer (N− in the case of an-FD-RCAT), forming a buried layer region underneath the P+ dopedregions 2824 for junction isolation, and connecting that buried regionto a thermal and electrical contact, similar to what is described forlayer 1606 and region 1646 in FIGS. 16A-G in the incorporated referencepending U.S. patent application Ser. No. 13/441,923 and U.S. PatentPublication 2012/0091587. Moreover, implants after the formation of theisolation regions 2805 may be annealed by optical (such as pulsed laser)means as previously described and the acceptor wafer metallization maybe protected by the shield/heat sink layer 2888. Furthermore, raisedsource and drain contact structures, such as etch and epi SiGe and SiC,may be utilized for strain and contact resistance improvements and thedamage from the processes may be optically annealed. Moreover, theoptical anneal may be performed at each sub-step as desired, or may bedone at prior to the HKMG deposition (such as after the dummy gate butbefore the HKMG formation), or various combinations. Moreover, multiplepulses of the laser may be utilized to improve the anneal, activation,and yield of the process. Many other modifications within the scope ofthe invention will suggest themselves to such skilled persons afterreading this specification. Thus the invention is to be limited only bythe appended claims.

A planar fully depleted n-channel MOSFET (FD-MOSFET) with an optionalintegrated heat shield/spreader suitable for a monolithic 3D IC may beconstructed as follows. The FD-MOSFET may provide an improved transistorvariability control and conduction channel electrostatic control, aswell as the ability to utilize an updoped channel, thereby improvingcarrier mobility. In addition, the FD-MOSFET does not demand doping orpocket implants in the channel to control the electrostaticcharacteristics and tune the threshold voltages. Sub-threshold slope,DIBL, and other short channel effects are greatly improved due to thefirm gate electrostatic control over the channel. Moreover, a heatspreading, heat conducting and/or optically reflecting material layer orlayers may be incorporated between the sensitive metal interconnectlayers and the layer or regions being optically irradiated and annealedto repair defects in the crystalline 3D-IC layers and regions and toactivate semiconductor dopants in the crystalline layers or regions of a3D-IC without harm to the sensitive metal interconnect and associateddielectrics. FIG. 29A-G illustrates an exemplary n-channel FD-MOSFETwhich may be constructed in a 3D stacked layer using procedures outlinedbelow and in U.S. Pat. Nos. 8,273,610, 9,099,526, 9,219,005, 8,557,632and 8,581,349. The contents of the foregoing applications areincorporated herein by reference.

As illustrated in FIG. 29A, a P− substrate donor wafer 2900 may beprocessed to include a wafer sized layer of doping across the wafer. Thechannel layer 2902 may be formed by ion implantation and thermal anneal.P− substrate donor wafer 2900 may include a crystalline material, forexample, mono-crystalline (single crystal) silicon. P− substrate donorwafer 2900 may be very lightly doped (less than 1e15 atoms/cm³) ornominally un-doped (less than 1e14 atoms/cm³) Channel layer 2902 mayhave additional ion implantation and anneal processing to provide adifferent dopant level than P− substrate donor wafer 2900 and may havegraded or various layers of doping concentration. The layer stack mayalternatively be formed by epitaxially deposited doped or undopedsilicon layers, or by a combination of epitaxy and implantation, or bylayer transfer. Annealing of implants and doping may include, forexample, conductive/inductive thermal, optical annealing techniques ortypes of Rapid Thermal Anneal (RTA or spike). The preferred crystallinechannel layer 2902 will be undoped to eventually create an FD-MOSFETtransistor with an updoped conduction channel.

As illustrated in FIG. 29B, the top surface of the P− substrate donorwafer 2900 layer stack may be prepared for oxide wafer bonding with adeposition of an oxide or by thermal oxidation of channel layer 2902 toform oxide layer 2980. A layer transfer demarcation plane (shown asdashed line) 2999 may be formed by hydrogen implantation or othermethods as described in the incorporated references. The P− substratedonor wafer 2900, such as surface 2982, and acceptor wafer 2910 may beprepared for wafer bonding as previously described and low temperature(less than approximately 400° C.) bonded. Acceptor wafer 2910, asdescribed in the incorporated references, may include, for example,transistors, circuitry, and metal, such as, for example, aluminum orcopper, interconnect wiring, a metal shield/heat sink layer or layers,and thru layer via metal interconnect strips or pads. Acceptor wafer2910 may be substantially comprised of a crystalline material, forexample mono-crystalline silicon or germanium, or may be an engineeredsubstrate/wafer such as, for example, an SOI (Silicon on Insulator)wafer or GeOI (Germanium on Insulator) substrate. Acceptor wafer 2910may include transistors such as, for example, MOSFETS, FD-MOSFETS,FinFets, FD-RCATs, BJTs, HEMTs, and/or HBTs. The portion of the channellayer 2902 and the P− substrate donor wafer 2900 that may be above (whenthe layer stack is flipped over and bonded to the acceptor wafer 2910)the layer transfer demarcation plane 2999 may be removed by cleaving orother low temperature processes as described in the incorporatedreferences, such as, for example, ion-cut with mechanical or thermalcleave or other layer transfer methods, thus forming remaining channellayer 2903. Damage/defects to crystalline structure of channel layer2902 may be annealed by some of the annealing methods described, forexample the short wavelength pulsed laser techniques, wherein thechannel layer 2902 or portions of channel layer 2902 may be heated todefect annealing temperatures, but the layer transfer demarcation plane2999 may be kept below the temperate for cleaving and/or significanthydrogen diffusion. The optical energy may be deposited in the upperlayer of the stack, for example near surface 2982, and annealing of aportion of channel layer 2902 may take place via heat diffusion.

As illustrated in FIG. 29C, oxide layer 2980 and remaining channel layer2903 have been layer transferred to acceptor wafer 2910. The top surfaceof remaining channel layer 2903 may be chemically or mechanicallypolished, and/or may be thinned by low temperature oxidation and stripprocesses, such as the TEL SPA tool radical oxidation and HF:H₂Osolutions as described herein and in referenced patents and patentapplications. Thru the processing, the wafer sized layer remainingchannel layer 2903 could be thinned from its original total thickness,and its final total thickness could be in the range of about 5 nm toabout 20 nm, for example, 5 nm, 7 nm, 10 nm, 12 nm, 15 nm, or 20 nm.Remaining channel layer 2903 may have a thickness and doping that mayallow fully-depleted channel operation when the FD-MOSFET transistor issubstantially completely formed. Acceptor wafer 2910 may include one ormore (two are shown in this example) shield/heat sink layers 2988, whichmay include materials such as, for example, Aluminum, Tungsten (arefractory metal), Copper, silicon or cobalt based silicides, or formsof carbon such as carbon nanotubes, and may be layered itself asdescribed in FIG. 50 of incorporated patent reference U.S. Pat. No.9,385,058. Each shield/heat sink layer 2988 may have a thickness rangeof about 50 nm to about 1 mm, for example, 50 nm, 100 nm, 200 nm, 300nm, 500 nm, 0.1 um, 1 um, 2 um, and 10 um. Shield/heat sink layer 2988may include isolation openings 2987, and alignment mark openings (notshown), which may be utilized for short wavelength alignment of toplayer (donor) processing to the acceptor wafer alignment marks (notshown). Shield/heat sink layer 2988 may include one or more shield pathconnects 2985 and shield path vias 2983. Shield path via 2983 maythermally and/or electrically couple and connect shield path connect2985 to acceptor wafer 2910 interconnect metallization layers such as,for example, exemplary acceptor metal interconnect 2981 (shown). Shieldpath connect 2985 may also thermally and/or electrically couple andconnect each shield/heat sink layer 2988 to the other and to acceptorwafer 2910 interconnect metallization layers such as, for example,acceptor metal interconnect 2981, thereby creating a heat conductionpath from the shield/heat sink layer 2988 to the acceptor substrate2995, and a heat sink (shown in FIG. 29G). Isolation openings 2987 mayinclude dielectric materials, similar to those of BEOL isolation 2996.Acceptor wafer 2910 may include first (acceptor) layer metalinterconnect 2991, acceptor wafer transistors and devices 2993, andacceptor substrate 2995. Various topside defect anneals may be utilized.For this illustration, an optical beam such as the laser annealingpreviously described is used. Optical anneal beams may be optimized tofocus light absorption and heat generation within or at the surface ofremaining channel layer 2903 and provide surface smoothing and/or defectannealing (defects may be from the cleave and/or the ion-cutimplantation) with exemplary smoothing/annealing ray 2966. The laserassisted smoothing/annealing with the absorbed heat generated byexemplary smoothing/annealing ray 2966 may also include a pre-heat ofthe bonded stack to, for example, about 100° C. to about 400° C., and/ora rapid thermal spike to temperatures above about 200° C. to about 600°C. Additionally, absorber layers or regions, for example, includingamorphous carbon, amorphous silicon, and phase changing materials (seeU.S. Pat. Nos. 6,635,588 and 6,479,821 to Hawryluk et al. for example),may be utilized to increase the efficiency of the optical energy capturein conversion to heat for the desired annealing or activation processes.Moreover, multiple pulses of the laser may be utilized to improve theanneal, activation, and yield of the process. Reflected ray 2963 may bereflected and/or absorbed by shield/heat sink layer 2988 regions thusblocking the optical absorption of ray blocked metal interconnect 2981.Annealing of dopants or annealing of damage, such as from the H cleaveimplant damage, may be also accomplished by a set of rays such as repairray 2965. Heat generated by absorbed photons from, for example,smoothing/annealing ray 2966, reflected ray 2963, and/or repair ray 2965may also be absorbed by shield/heat sink layer 2988 regions anddissipated laterally and may keep the temperature of underlying metallayers, such as metal interconnect 2981, and other metal layers belowit, cooler and prevent damage. Shield/heat sink layer 2988 andassociated dielectrics may laterally spread and conduct the heatgenerated by the topside defect anneal, and in conjunction with thedielectric materials (low heat conductivity) above and below shield/heatsink layer 2988, keep the interconnect metals and low-k dielectrics ofthe acceptor wafer interconnect layers cooler than a damage temperature,such as, for example, 400° C. A second layer of shield/heat sink layer2988 may be constructed (shown) with a low heat conductive materialsandwiched between the two heat sink layers, such as silicon oxide orcarbon doped ‘low-k’ silicon oxides, for improved thermal protection ofthe acceptor wafer interconnect layers, metal and dielectrics.Shield/heat sink layer 2988 may act as a heat spreader. Electricallyconductive materials may be used for the two layers of shield/heat sinklayer 2988 and thus may provide, for example, a Vss and a Vdd planeand/or grid that may be connected to the donor layer transistors above,as well may be connected to the acceptor wafer transistors below, and/ormay provide below transferred layer device interconnection. Noise on thepower grids, such as the Vss and Vdd plane power conducting lines/wires,may be mitigated by attaching/connecting decoupling capacitors onto thepower conducting lines of the grids. The decoupling caps, which may bewithin the second layer (donor, for example, donor wafer devicestructures) or first layer (acceptor, for example acceptor wafertransistors and devices 2993), may include, for example, trenchcapacitors such as described by Pei, C., et al., “A novel, low-cost deeptrench decoupling capacitor for high-performance, low-power bulk CMOSapplications,” ICSICT (9^(th) International Conference on Solid-Stateand Integrated-Circuit Technology) 2008, October 2008, pp. 1146-1149, ofIBM. The decoupling capacitors may include, for example, planarcapacitors, such as poly to substrate or poly to poly, or MiM capacitors(Metal-Insulator-Metal). Shield/heat sink layer 2988 may includematerials with a high thermal conductivity greater than 10 W/m-K, forexample, copper (about 400 W/m-K), aluminum (about 237 W/m-K), Tungsten(about 173 W/m-K), Plasma Enhanced Chemical Vapor Deposited Diamond LikeCarbon-PECVD DLC (about 1000 W/m-K), and Chemical Vapor Deposited (CVD)graphene (about 5000 W/m-K). Shield/heat sink layer 2988 may besandwiched and/or substantially enclosed by materials with a low thermalconductivity (less than 10 W/m-K), for example, silicon dioxide (about1.4 W/m-K). The sandwiching of high and low thermal conductivitymaterials in layers, such as shield/heat sink layer 2988 and under &overlying dielectric layers, spreads the localized heat/light energy ofthe topside anneal laterally and protects the underlying layers ofinterconnect metallization & dielectrics, such as in the acceptor wafer2910, from harmful temperatures or damage. When there may be more thanone shield/heat sink layer 2988 in the device, the heat conducting layerclosest to the second crystalline layer or oxide layer 2980 may beconstructed with a different material, for example a high melting pointmaterial, for example a refractory metal such as tungsten, than theother heat conducting layer or layers, which may be constructed with,for example, a lower melting point material, for example, such asaluminum or copper. Now transistors may be formed with low effectivetemperature (less than approximately 400° C. exposure to the acceptorwafer 2910 sensitive layers, such as interconnect and device layers)processing, and may be aligned to the acceptor wafer alignment marks(not shown) as described in the incorporated references. This mayinclude further optical defect annealing or dopant activation steps. Thedonor wafer 2900 may now also be processed, such as smoothing andannealing, and reused for additional layer transfers. The insulatorlayer, such as deposited bonding oxides (for example oxide layer 2980)and/or before bonding preparation existing oxides (for example the BEOLisolation 2996 on top of the topmost metal layer of shield/heat sinklayer 2988), between the donor wafer transferred monocrystalline layerand the acceptor wafer topmost metal layer, may include thicknesses ofless than 1 um, less than 500 nm, less than 400 nm, less than 300 nm,less than 200 nm, or less than 100 nm.

As illustrated in FIG. 29D, transistor isolation regions 2905 may beformed by mask defining and plasma/RIE etching remaining channel layer2903 substantially to the top of oxide layer 2980 (not shown),substantially into oxide layer 2980, or into a portion of the upperoxide layer of acceptor wafer 2910 (not shown). Thus channel region 2923may be formed, which may substantially form the transistor body. Alow-temperature gap fill dielectric, such as SACVD oxide, may bedeposited and chemically mechanically polished, the oxide remaining inisolation regions 2905. An optical step, such as illustrated byexemplary STI ray 2967, may be performed to anneal etch damage anddensify the STI oxide in isolation regions 2905. The dopingconcentration of the channel region 2923 may include gradients ofconcentration or layers of differing doping concentrations. Anyadditional doping, such as ion-implanted channel implants, may beactivated and annealed with optical annealing, such as illustrated byexemplary implant ray 2969, as described herein. The optical anneal,such as exemplary STI ray 2967, and/or exemplary implant ray 2969 may beperformed at separate times and processing parameters (such as laserenergy, frequency, etc.) or may be done in combination or as one opticalanneal. Optical absorber and or reflective layers or regions may beemployed to enhance the anneal and/or protect the underlying sensitivestructures. Moreover, multiple pulses of the laser may be utilized toimprove the anneal, activation, and yield of the process.

As illustrated in FIG. 29E, a transistor forming process, such as aconventional HKMG with raised source and drains (S/D), may be performed.For example, a dummy gate stack (not shown), utilizing oxide andpolysilicon, may be formed, gate spacers 2930 may be formed, raised S/Dregions 2932 and channel stressors may be formed by etch and epitaxialdeposition, for example, of SiGe and/or SiC depending on P or N channel,LDD and S/D ion-implantations may be performed, and first ILD 2936 maybe deposited and CMP'd to expose the tops of the dummy gates. Thustransistor channel 2933 and S/D & LDD regions 2935 may be formed. Thedummy gate stack may be removed and a gate dielectric 2907 may be formedand a gate metal material gate electrode 2908, including a layer ofproper work function metal (Ti_(x)Al_(y),N_(z) for example) and aconductive fill, such as aluminum, and may be deposited and CMP'd. Thegate dielectric 2907 may be an atomic layer deposited (ALD) gatedielectric that may be paired with a work function specific gate metalin the industry standard high k metal gate process schemes, for example,as described in the incorporated references. Alternatively, the gatedielectric 2907 may be formed with a low temperature processesincluding, for example, LPCVD SiO₂ oxide deposition (see Ahn, J., etal., “High-quality MOSFET's with ultrathin LPCVD gate SiO2,” IEEEElectron Device Lett., vol. 13, no. 4, pp. 186-188, April 1992) or lowtemperature microwave plasma oxidation of the silicon surfaces (see Kim,J. Y., et al., “The excellent scalability of the RCAT(recess-channel-array-transistor) technology for sub-70 nm DRAM featuresize and beyond,” 2005 IEEE VLSI-TSA International Symposium, pp. 33-29,25-27 Apr. 2005) and a gate material with proper work function and lessthan approximately 400° C. deposition temperature such as, for example,tungsten or aluminum may be deposited. An optical step, such asrepresented by exemplary anneal ray 2921, may be performed to densifyand/or remove defects from gate dielectric 2907, anneal defects andactivate dopants such as LDD and S/D implants, densify the first ILD2936, form DSS junctions (Dopant Segregated Schottky such as NiSi₂),and/or form contact and S/D silicides (not shown). The optical annealmay be performed at each sub-step as desired, or may be done at prior tothe HKMG deposition (such as after the dummy gate but before the HKMGformation), or various combinations. Moreover, multiple pulses of thelaser may be utilized to improve the anneal, activation, and yield ofthe process. Raised S/D regions 2932 may be formed by low temperature(less than 400° C.) deposition of in-situ doped polysilicon or amorphoussilicon into the S/D openings, an optical anneal to further crystallizeand dopant activate the raised S/D material, and removal of excessraised S/D material

As illustrated in FIG. 29F, a low temperature thick oxide 2909 may bedeposited and planarized. Source, gate, and drain contacts openings maybe masked and etched preparing the transistors to be connected viametallization. Thus gate contact 2911 connects to gate electrode 2908,and source & drain contacts 2940 connect to raised S/D regions 2932. Anoptical step, such as illustrated by exemplary ILD anneal ray 2951, maybe performed to anneal contact etch damage and densify the thick oxide2909.

As illustrated in FIG. 29G, thru layer vias (TLVs) 2960 may be formed byetching thick oxide 2909, first ILD 2936, isolation regions 2905, oxidelayer 2980, into a portion of the upper oxide layer BEOL isolation 2996of acceptor wafer 2910 BEOL, and filling with an electrically andthermally conducting material (such as tungsten or cooper) or anelectrically non-conducting but thermally conducting material (such asdescribed elsewhere within). Second device layer metal interconnect 2961may be formed by conventional processing. TLVs 2960 may be constructedof thermally conductive but not electrically conductive materials, forexample, DLC (Diamond Like Carbon), and may connect the FD-MOSFETtransistor device and other devices on the top (second) crystallinelayer thermally to shield/heat sink layer 2988. TLVs 2960 may beconstructed out of electrically and thermally conductive materials, suchas Tungsten, Copper, or aluminum, and may provide a thermal andelectrical connection path from the FD-MOSFET transistor device andother devices on the top (second) crystalline layer to shield/heat sinklayer 2988, which may be a ground or Vdd plane in the design/layout.TLVs 2960 may be also constructed in the device scribelanes(pre-designed in base layers or potential dicelines) to provide thermalconduction to the heat sink, and may be sawed/diced off when the waferis diced for packaging not shown). Shield/heat sink layer 2988 may beconfigured to act (or adapted to act) as an emf (electro-motive force)shield to prevent direct layer to layer cross-talk between transistorsin the donor wafer layer and transistors in the acceptor wafer. Inaddition to static ground or Vdd biasing, shield/heat sink layer 2988may be actively biased with an anti-interference signal from circuitryresiding on, for example, a layer of the 3D-IC or off chip. The formedFD-MOSFET transistor device may include semiconductor regions whereinthe dopant concentration of neighboring regions of the transistor in thehorizontal plane, such as traversed by exemplary dopant plane 2934, mayhave regions, for example, transistor channel 2933 and S/D & LDD regions2935, that differ substantially in dopant concentration, for example, a10 times greater doping concentration in S/D & LDD regions 2935 than intransistor channel 2933, and/or may have a different dopant type, suchas, for example p-type or n-type dopant, and/or may be doped andsubstantially undoped in the neighboring regions. For example,transistor channel 2933 may be very lightly doped (less than 1e15atoms/cm³) or nominally un-doped (less than 1e14 atoms/cm³) and S/D &LDD regions 2935 may be doped at greater than 1e15 atoms/cm³ or greaterthan 1e16 atoms/cm³. For example, transistor channel 2933 may be dopedwith p-type dopant and S/D & LDD regions 2935 may be doped with n-typedopant.

A thermal conduction path may be constructed from the devices in theupper layer, the transferred donor layer and formed transistors, to theacceptor wafer substrate and associated heat sink. The thermalconduction path from the FD-MOSFET transistor device and other deviceson the top (second) crystalline layer, for example, raised S/D regions2932, to the acceptor wafer heat sink 2997 may include source & draincontacts 2940, second device layer metal interconnect 2961, TLV 2960,shield path connect 2985 (shown as twice), shield path via 2983 (shownas twice), metal interconnect 2981, first (acceptor) layer metalinterconnect 2991, acceptor wafer transistors and devices 2993, andacceptor substrate 2995. The elements of the thermal conduction path mayinclude materials that have a thermal conductivity greater than 10W/m-K, for example, copper (about 400 W/m-K), aluminum (about 237W/m-K), and Tungsten (about 173 W/m-K), and may include material withthermal conductivity lower than 10 W/m-K but have a high heat transfercapacity due to the wide area available for heat transfer and thicknessof the structure (Fourier's Law), such as, for example, acceptorsubstrate 2995. The elements of the thermal conduction path may includematerials that are thermally conductive but may not be substantiallyelectrically conductive, for example, Plasma Enhanced Chemical VaporDeposited Diamond Like Carbon-PECVD DLC (about 1000 W/m-K), and ChemicalVapor Deposited (CVD) graphene (about 5000 W/m-K). The acceptor waferinterconnects may be substantially surrounded by BEOL isolation 2996dielectric. The heat removal apparatus, which may include acceptor waferheat sink 2997, may include an external surface from which heat transfermay take place by methods such as air cooling, liquid cooling, orattachment to another heat sink or heat spreader structure.

Furthermore, some or all of the layers utilized as shield/heat sinklayer 2988, which may include shapes of material such as the strips orfingers as illustrated in FIG. 27B-1 , may be driven by a portion of thesecond layer transistors and circuits (within the transferred donorwafer layer or layers) or the acceptor wafer transistors and circuits,to provide a programmable back-bias to at least a portion of the secondlayer transistors. The programmable back bias may utilize a circuit todo so, for example, such as shown in FIG. 17B of U.S. Pat. No.8,273,610, the contents incorporated herein by reference; wherein the‘Primary’ layer may be the second layer of transistors for which theback-bias is being provided, the ‘Foundation’ layer could be either thesecond layer transistors (donor) or first layer transistors (acceptor),and the routing metal lines connections 1723 and 1724 may includeportions of the shield/heat sink layer 2988 layer or layers. Moreover,some or all of the layers utilized as shield/heat sink layer 2988, whichmay include strips or fingers as illustrated in FIG. 27B-1 , may bedriven by a portion of the second layer transistors and circuits (withinthe transferred donor wafer layer or layers) or the acceptor wafertransistors and circuits to provide a programmable power supply to atleast a portion of the second layer transistors. The programmable powersupply may utilize a circuit to do so, for example, such as shown inFIG. 17C of U.S. Pat. No. 8,273,610, the contents incorporated herein byreference; wherein the ‘Primary’ layer may be the second layer oftransistors for which the programmable power supplies are being providedto, the ‘Foundation’ layer could be either the second layer transistors(donor) or first layer transistors (acceptor), and the routing metalline connections from Vout to the various second layer transistors mayinclude portions of the shield/heat sink layer 2988 layer or layers. TheVsupply on line 17C12 and the control signals on control line 17C16 maybe controlled by and/or generated in the second layer transistors (forexample donor wafer device structures such as the FD-MOSFETs formed asdescribed in relation to FIG. 29 ) or first layer transistors (acceptor,for example acceptor wafer transistors and devices 2993), or off chipcircuits. Furthermore, some or all of the layers utilized as shield/heatsink layer 2988, which may include strips or fingers as illustrated inFIG. 27B-1 or other shapes such as those in FIG. 27B, may be utilized todistribute independent power supplies to various portions of the secondlayer transistors (for example donor wafer device structures such as theFD-MOSFETs formed as described in relation to FIG. 29 of incorporatedpatent reference U.S. Pat. No. 9,385,058) or first layer transistors(acceptor, for example acceptor wafer transistors and devices 2993 ofincorporated patent reference U.S. Pat. No. 9,385,058) and circuits; forexample, one power supply and/or voltage may be routed to the sequentiallogic circuits of the second layer and a different power supply and/orvoltage routed to the combinatorial logic circuits of the second layer.Moreover, the power distribution circuits/grid may be designed so thatVdd may have a different value for each stack layer. Patterning ofshield/heat sink layer 2988 or layers can impact their heat-shieldingcapacity. This impact may be mitigated, for example, by enhancing thetop shield/heat sink layer 2988 areal density, creating more of thesecondary shield/heat sink layers 2988, or attending to special CADrules regarding their metal density, similar to CAD rules that arerequired to accommodate Chemical-Mechanical Planarization (CMP). Theseconstraints would be integrated into a design and layout EDA tool.Second layer metallization and power grid wires (such as second devicelayer metal interconnect 2961) may be constructed thicker and wider thanthe first layer metal interconnect (such as metal interconnect 2981),and hence have a higher current conduction capacity. Moreover, thesecond layer of circuits and transistors, for example, for example donorwafer device structures such as the FD-MOSFETs formed as described inrelation to FIG. 29 , may include I/O logic devices, such as SerDes(Serialiser/Deserialiser), and conductive bond pads (not shown) (hereinsuch as FIG. 33 ). The output or input conductive pads of the I/Ocircuits may be coupled, for example by bonded wires, to externaldevices. The output or input conductive pads may also act as a contactport for the 3D device output to connect to external devices. The emfgenerated by the I/O circuits could be shielded from the other layers inthe stack by use of, for example, the shield/heat sink layer 2988.Placement of the I/O circuits on the same stack layer as the conductivebond pad may enable close coupling of the desired I/O energy and lowersignal loss. Furthermore, the second layer of circuits and transistors,for example donor wafer device structures such as the FD-MOSFETs formedas described in relation to FIG. 29 , may include RF (Radio Frequency)circuits and/or at least one antenna. For example, the second layer ofcircuits and transistors may include RF circuits to enable an off-chipcommunication capability to external devices, for example, a wirelesscommunication circuit or circuits such as a Bluetooth protocol orcapacitive coupling. The emf generated by the RF circuits could beshielded from the other layers in the stack by use of, for example, theshield/heat sink layer 2988.

TLVs 2960 may be formed through the transferred layers. As thetransferred layers may be thin, on the order of about 200 nm or less inthickness, the TLVs may be easily manufactured as a typical metal tometal via may be, and said TLV may have state of the art diameters suchas nanometers or tens to a few hundreds of nanometers, such as, forexample about 150 nm or about 100 nm or about 50 nm. The thinner thetransferred layers, the smaller the thru layer via diameter obtainable,which may result from maintaining manufacturable via aspect ratios. Thethickness of the layer or layers transferred according to someembodiments of the invention may be designed as such to match and enablethe most suitable obtainable lithographic resolution (and enable the useof conventional state of the art lithographic tools), such as, forexample, less than about 10 nm, 14 nm, 22 nm or 28 nm linewidthresolution and alignment capability, such as, for example, less thanabout 5 nm, 10 nm, 20 nm, or 40 nm alignment accuracy/precision/error,of the manufacturing process employed to create the thru layer vias orany other structures on the transferred layer or layers.

As illustrated in FIG. 29G-1 , at least one conductive bond pad 2964 forinterfacing electrically (and may thermally) to external devices may beformed on top of the completed device and may include at least one metallayer of second device layer metal interconnect 2961. Bond pad 2964 mayoverlay second device layer metal interconnect 2961 or a portion of(some of the metal and insulator layers of) second device layer metalinterconnect 2961. Bond pad 2964 may be directly aligned to the acceptorwafer alignment marks (not shown) and the I/O driver circuitry may beformed by the second layer (donor) transistors, for example, donor waferdevice structures such as the FD-MOSFETs formed as described in relationto FIG. 29 . Bond pad 2964 may be connected to the second layertransistors thru the second device layer metal interconnect 2961 whichmay include vias 2962. The I/O driver circuitry may be formed bytransistors from the acceptor wafer transistors and devices 2993, orfrom transistors in other strata if the 3DIC device has more than twolayers of transistors. I/O pad control metal segment 2967 may be formeddirectly underneath bond pad 2964 and may influence the noise and ESD(Electro Static Discharge) characteristics of bond pad 2964. The emfinfluence of I/O pad control metal segment 2967 may be controlled bycircuitry formed from a portion of the second layer transistors. I/O padcontrol metal segment 2967 may be formed with second device layer metalinterconnect 2961. Furthermore, metal segment 2989 of the topmostshield/heat sink layer 2988 may be used to influence the FD-MOSFETtransistor or transistors above it by emf, and influence the noise andESD (Electro Static Discharge) characteristics of bond pad 2964. Metalsegment 2989 may be controlled by second layer (donor) transistors, forexample, donor wafer device structures such as the FD-MOSFETs formed asdescribed in relation to FIG. 29 and/or by transistors from the acceptorwafer transistors and devices 2993, or from transistors in other strataif the 3DIC device has more than two layers of transistors. Power fromexternal sources may be routed to conductive bond pad 2964 to the 3Ddevice, wherein at least a portion of the second layer interconnectionssuch as second device layer metal interconnect 2961 and associated vias,may be constructed as a power distribution grid/network, and the powerdistribution grid/network may be connected electrically and thermallyvia TLVs 2960 to the transistor layer below's (such as acceptor wafertransistors and devices 2993) power distribution grid/network, the powerdistribution grid/network may include for example, shield/heat sinklayer 2988 or Vss/Vdd strategy as described herein at least FIG. 32 ,and it's associated portion of a thermal conduction path (shield pathconnect 2985, shield path vias 2983, metal interconnect 2981, first(acceptor) layer metal interconnect 2991) to acceptor wafer transistorsand devices 2993, acceptor substrate 2995, and acceptor wafer heat sink2997.

Formation of CMOS in one transferred layer and the orthogonal connectstrip methodology may be found as illustrated in at least FIGS. 30-33,73-80, and 94 and related specification sections of U.S. Pat. No.8,273,610, and may be applied to at least the FIG. 29 formationtechniques herein. Transferred layer or layers may have regions of STIor other transistor elements within it or on it when transferred, butwould then use alignment and connection schemes for layer transfer ofpatterned layers as described in incorporated patent references.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 29A through 29G are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations are possible such as, for example, a p-channel FD-MOSFET maybe formed with changing the types of dopings appropriately. Moreover,the P− substrate donor wafer 2900 may be n type or un-doped.Furthermore, isolation regions 2905 may be formed by a hard mask definedprocess flow, wherein a hard mask stack, such as, for example, siliconoxide and silicon nitride layers, or silicon oxide and amorphous carbonlayers, may be utilized. Moreover, CMOS FD MOSFET s may be constructedwith n-MOSFETs in a first mono-crystalline silicon layer and p-MOSFET sin a second mono-crystalline layer, which may include differentcrystalline orientations of the mono-crystalline silicon layers, such asfor example, <100>, <111> or <551>, and may include different contactsilicides for optimum contact resistance to p or n type source, drains,and gates. Further, dopant segregation techniques (DST) may be utilizedto efficiently modulate the source and drain Schottky barrier height forboth p and n type junctions formed. Furthermore, raised source and draincontact structures, such as etch and epi SiGe and SiC, may be utilizedfor strain and contact resistance improvements and the damage from theprocesses may be optically annealed. Many other modifications within thescope of the invention will suggest themselves to such skilled personsafter reading this specification. Thus the invention is to be limitedonly by the appended claims.

A planar fully depleted n-channel MOSFET (FD-MOSFET) with an optionalintegrated heat shield/spreader and back planes and body bias tapssuitable for a monolithic 3D IC may be constructed as follows. TheFD-MOSFET may provide an improved transistor variability control andconduction channel electrostatic control, as well as the ability toutilize an updoped channel, thereby improving carrier mobility. Inaddition, the FD-MOSFET does not demand doping or pocket implants in thechannel to control the electrostatic characteristics and tune thethreshold voltages. Sub-threshold slope, DIBL, and other short channeleffects are greatly improved due to the firm gate electrostatic controlover the channel. In this embodiment, a ground plane is constructed thatmay provide improved electrostatics and/or Vt adjustment and/orback-bias of the FD-MOSFET. In addition, selective regions may beconstructed to provide body bias and/or partially depleted/bulk-liketransistors. Moreover, a heat spreading, heat conducting and/oroptically reflecting material layer or layers may be incorporatedbetween the sensitive metal interconnect layers and the layer or regionsbeing optically irradiated and annealed to repair defects in thecrystalline 3D-IC layers and regions and to activate semiconductordopants in the crystalline layers or regions of a 3D-IC without harm tothe sensitive metal interconnect and associated dielectrics. FIG. 30A-Gillustrates an exemplary n-channel FD-MOSFET which may be constructed ina 3D stacked layer using procedures outlined below and in U.S. Pat. Nos.8,273,610, 9,099,526, 9,219,005, 8,557,632 and 8,581,349. The contentsof the foregoing applications are incorporated herein by reference.

As illustrated in FIG. 30A, SOI donor wafer substrate 3000 may includeback channel layer 3002 above Buried Oxide BOX layer 3001. Back channellayer 3002 may be doped by ion implantation and thermal anneal, mayinclude a crystalline material, for example, mono-crystalline (singlecrystal) silicon and may be heavily doped (greater than 1e16 atoms/cm³),lightly doped (less than 1e16 atoms/cm³) or nominally un-doped (lessthan 1e14 atoms/cm³). SOI donor wafer substrate 3000 may include acrystalline material, for example, mono-crystalline (single crystal)silicon and at least the upper layer near BOX layer 3001 may be verylightly doped (less than 1e15 atoms/cm³) or nominally un-doped (lessthan 1e14 atoms/cm³). Back channel layer 3002 may have additional ionimplantation and anneal processing to provide a different dopant levelthan SOI donor wafer substrate 3000 and may have graded or variouslayers of doping concentration. SOI donor wafer substrate 3000 may haveadditional ion implantation and anneal processing to provide a differentdopant level than back channel layer 3002 and may have graded or variouslayers of doping concentration. The layer stack may alternatively beformed by epitaxially deposited doped or undoped silicon layers, or by acombination of epitaxy and implantation, or by layer transfer. Annealingof implants and doping may include, for example, conductive/inductivethermal, optical annealing techniques or types of Rapid Thermal Anneal(RTA or spike). The preferred at least top of SOI donor wafer substrate3000 doping will be undoped to eventually create an FD-MOSFET transistorwith an updoped conduction channel SOI donor wafer may be constructed bylayer transfer techniques described herein or elsewhere as known in theart, or by laser annealed SIMOX at a post donor layer transfer toacceptor wafer step. BOX layer 3001 may be thin enough to provide foreffective back and/or body bias, for example, 25 nm, or 20 nm, or 10 nm,or 35 nm.

As illustrated in FIG. 30B, the top surface of the SOI donor wafersubstrate 3000 layer stack may be prepared for oxide wafer bonding witha deposition of an oxide or by thermal oxidation of back channel layer3002 to form oxide layer 3080. A layer transfer demarcation plane (shownas dashed line) 3099 may be formed by hydrogen implantation or othermethods as described in the incorporated references, and may residewithin the SOI donor wafer substrate 3000. The SOI donor wafer substrate3000 stack, such as surface 3082, and acceptor wafer 3010 may beprepared for wafer bonding as previously described and low temperature(less than approximately 400° C.) bonded. Acceptor wafer 3010, asdescribed in the incorporated references, may include, for example,transistors, circuitry, and metal, such as, for example, aluminum orcopper, interconnect wiring, a metal shield/heat sink layer or layers,and thru layer via metal interconnect strips or pads. Acceptor wafer3010 may be substantially comprised of a crystalline material, forexample mono-crystalline silicon or germanium, or may be an engineeredsubstrate/wafer such as, for example, an SOI (Silicon on Insulator)wafer or GeOI (Germanium on Insulator) substrate. Acceptor wafer 3010may include transistors such as, for example, MOSFETS, FD-MOSFETS,FinFets, FD-RCATs, BJTs, HEMTs, and/or HBTs. The portion of the SOIdonor wafer substrate 3000 that may be above (when the layer stack isflipped over and bonded to the acceptor wafer 3010) the layer transferdemarcation plane 3099 may be removed by cleaving or other lowtemperature processes as described in the incorporated references, suchas, for example, ion-cut with mechanical or thermal cleave or otherlayer transfer methods, thus forming remaining channel layer 3003.Damage/defects to crystalline structure of back channel layer 3002 maybe annealed by some of the annealing methods described, for example theshort wavelength pulsed laser techniques, wherein the back channel layer3002 and/or portions of the SOI donor wafer substrate 3000 may be heatedto defect annealing temperatures, but the layer transfer demarcationplane 3099 may be kept below the temperate for cleaving and/orsignificant hydrogen diffusion. The optical energy may be deposited inthe upper layer of the stack, for example near surface 3082, andannealing of back channel layer 3002 and/or portions of the SOI donorwafer substrate 3000 may take place via heat diffusion. Moreover,multiple pulses of the laser may be utilized to improve the anneal,activation, and yield of the process and/or to control the maximumtemperature of various structures in the stack.

As illustrated in FIG. 30C, oxide layer 3080, back channel layer 3002,BOX layer 3001 and channel layer 3003 may be layer transferred toacceptor wafer 3010. The top surface of channel layer 3003 may bechemically or mechanically polished, and/or may be thinned by lowtemperature oxidation and strip processes, such as the TEL SPA toolradical oxidation and HF:H₂O solutions as described herein and inreferenced patents and patent applications. Thru the processing, thewafer sized layer channel layer 3003 could be thinned from its originaltotal thickness, and its final total thickness could be in the range ofabout 5 nm to about 20 nm, for example, 5 nm, 7 nm, 10 nm, 12 nm, 15 nm,or 20 nm. Channel layer 3003 may have a thickness and/or doping that mayallow fully-depleted channel operation when the FD-MOSFET transistor issubstantially completely formed. Acceptor wafer 3010 may include one ormore (two are shown in this example) shield/heat sink layers 3088, whichmay include materials such as, for example, Aluminum, Tungsten (arefractory metal), Copper, silicon or cobalt based silicides, or formsof carbon such as carbon nanotubes, and may be layered itself asdescribed in FIG. 50 of incorporated patent reference U.S. Pat. No.9,385,058. Each shield/heat sink layer 3088 may have a thickness rangeof about 50 nm to about 1 mm, for example, 50 nm, 100 nm, 200 nm, 300nm, 500 nm, 0.1 um, 1 um, 2 um, and 10 um. Shield/heat sink layer 3088may include isolation openings 3087, and alignment mark openings (notshown), which may be utilized for short wavelength alignment of toplayer (donor) processing to the acceptor wafer alignment marks (notshown). Shield/heat sink layer 3088 may include one or more shield pathconnects 3085 and shield path vias 3083. Shield path via 3083 maythermally and/or electrically couple and connect shield path connect3085 to acceptor wafer 3010 interconnect metallization layers such as,for example, exemplary acceptor metal interconnect 3081 (shown). Shieldpath connect 3085 may also thermally and/or electrically couple andconnect each shield/heat sink layer 3088 to the other and to acceptorwafer 3010 interconnect metallization layers such as, for example,acceptor metal interconnect 3081, thereby creating a heat conductionpath from the shield/heat sink layer 3088 to the acceptor substrate3095, and a heat sink (shown in FIG. 30G). Isolation openings 3087 mayinclude dielectric materials, similar to those of BEOL isolation 3096.Acceptor wafer 3010 may include first (acceptor) layer metalinterconnect 3091, acceptor wafer transistors and devices 3093, andacceptor substrate 3095. Various topside defect anneals may be utilized.For this illustration, an optical beam such as the laser annealingpreviously described is used. Optical anneal beams may be optimized tofocus light absorption and heat generation within or at the surface ofchannel layer 3003 and provide surface smoothing and/or defect annealing(defects may be from the cleave and/or the ion-cut implantation) withexemplary smoothing/annealing ray 3066. The laser assistedsmoothing/annealing with the absorbed heat generated by exemplarysmoothing/annealing ray 3066 may also include a pre-heat of the bondedstack to, for example, about 100° C. to about 400° C., and/or a rapidthermal spike to temperatures above about 200° C. to about 600° C.Additionally, absorber layers or regions, for example, includingamorphous carbon, amorphous silicon, and phase changing materials (seeU.S. Pat. Nos. 6,635,588 and 6,479,821 to Hawryluk et al. for example),may be utilized to increase the efficiency of the optical energy capturein conversion to heat for the desired annealing or activation processes.Moreover, multiple pulses of the laser may be utilized to improve theanneal, activation, and yield of the process. Reflected ray 3063 may bereflected and/or absorbed by shield/heat sink layer 3088 regions thusblocking the optical absorption of ray blocked metal interconnect 3081.Annealing of dopants or annealing of damage in back channel layer 3002and/or BOX 3010 and/or channel layer 3003, such as from the H cleaveimplant damage, may be also accomplished by a set of rays such as repairray 3065, illustrated is focused on back channel layer 3002. Heatgenerated by absorbed photons from, for example, smoothing/annealing ray3066, reflected ray 3063, and/or repair ray 3065 may also be absorbed byshield/heat sink layer 3088 regions and dissipated laterally and maykeep the temperature of underlying metal layers, such as metalinterconnect 3081, and other metal layers below it, cooler and preventdamage Shield/heat sink layer 3088 and associated dielectrics maylaterally spread and conduct the heat generated by the topside defectanneal, and in conjunction with the dielectric materials (low heatconductivity) above and below shield/heat sink layer 3088, keep theinterconnect metals and low-k dielectrics of the acceptor waferinterconnect layers cooler than a damage temperature, such as, forexample, 400° C. A second layer of shield/heat sink layer 3088 may beconstructed (shown) with a low heat conductive material sandwichedbetween the two heat sink layers, such as silicon oxide or carbon doped‘low-k’ silicon oxides, for improved thermal protection of the acceptorwafer interconnect layers, metal and dielectrics. Shield/heat sink layer3088 may act as a heat spreader. Electrically conductive materials maybe used for the two layers of shield/heat sink layer 3088 and thus mayprovide, for example, a Vss and a Vdd plane and/or grid that may beconnected to the donor layer transistors above, as well may be connectedto the acceptor wafer transistors below, and/or may provide belowtransferred layer device interconnection. Noise on the power grids, suchas the Vss and Vdd plane power conducting lines/wires, may be mitigatedby attaching/connecting decoupling capacitors onto the power conductinglines of the grids. The decoupling caps, which may be within the secondlayer (donor, for example, donor wafer device structures) or first layer(acceptor, for example acceptor wafer transistors and devices 3093), mayinclude, for example, trench capacitors such as described by Pei, C., etal., “A novel, low-cost deep trench decoupling capacitor forhigh-performance, low-power bulk CMOS applications,” ICSICT (9^(th)International Conference on Solid-State and Integrated-CircuitTechnology) 2008, October 2008, pp. 1146-1149, of IBM. The decouplingcapacitors may include, for example, planar capacitors, such as poly tosubstrate or poly to poly, or MiM capacitors (Metal-Insulator-Metal).Shield/heat sink layer 3088 may include materials with a high thermalconductivity greater than 10 W/m-K, for example, copper (about 400W/m-K), aluminum (about 237 W/m-K), Tungsten (about 173 W/m-K), PlasmaEnhanced Chemical Vapor Deposited Diamond Like Carbon-PECVD DLC (about1000 W/m-K), and Chemical Vapor Deposited (CVD) graphene (about 5000W/m-K). Shield/heat sink layer 3088 may be sandwiched and/orsubstantially enclosed by materials with a low thermal conductivity(less than 10 W/m-K), for example, silicon dioxide (about 1.4 W/m-K).The sandwiching of high and low thermal conductivity materials inlayers, such as shield/heat sink layer 3088 and under & overlyingdielectric layers, spreads the localized heat/light energy of thetopside anneal laterally and protects the underlying layers ofinterconnect metallization & dielectrics, such as in the acceptor wafer3010, from harmful temperatures or damage. When there may be more thanone shield/heat sink layer 3088 in the device, the heat conducting layerclosest to the second crystalline layer or oxide layer 3080 may beconstructed with a different material, for example a high melting pointmaterial, for example a refractory metal such as tungsten, than theother heat conducting layer or layers, which may be constructed with,for example, a lower melting point material, for example such asaluminum or copper. Now transistors may be formed with low effectivetemperature (less than approximately 400° C. exposure to the acceptorwafer 3010 sensitive layers, such as interconnect and device layers)processing, and may be aligned to the acceptor wafer alignment marks(not shown) as described in the incorporated references. This mayinclude further optical defect annealing or dopant activation steps. Theremaining SOI donor wafer substrate 3000 may now also be processed, suchas smoothing and annealing, and reused for additional layer transfers.The insulator layer, such as deposited bonding oxides (for example oxidelayer 3080) and/or before bonding preparation existing oxides (forexample the BEOL isolation 3096 on top of the topmost metal layer ofshield/heat sink layer 3088), between the donor wafer transferredmonocrystalline layer and the acceptor wafer topmost metal layer, mayinclude thicknesses of less than 1 um, less than 500 nm, less than 400nm, less than 300 nm, less than 200 nm, or less than 100 nm.

As illustrated in FIG. 30D, transistor and back channel isolationregions 3005 and/or transistor isolation regions 3086 may be formed.Transistor isolation region 3086 may be formed by mask defining andplasma/RIE etching channel layer 3003, substantially to the top of BOXlayer 3001 (not shown), substantially into BOX layer 3001, or backchannel layer 3002 (not shown). Transistor and back channel isolationregions 3005 may be formed by mask defining and plasma/RIE etchingchannel layer 3003, BOX layer 3001 and back channel layer 3002,substantially to the top of oxide layer 3080 (not shown), substantiallyinto oxide layer 3080, or further into the top BEOL dielectric layer inacceptor wafer 3010 (not shown). Thus channel region 3023 may be formed,which may substantially form the transistor body, back-channel region3022 may be formed, which may provide a back bias and/or Vt control bydoping or bias to one or more channel regions 3023, and BOX region 3031.Back-channel region 3022 may be ion implanted for Vt control and/or bodybias efficiency. A low-temperature gap fill dielectric, such as SACVDoxide, may be deposited and chemically mechanically polished, the oxideremaining in transistor and back channel isolation regions 3005 andtransistor isolation regions 3086. Back-channel region 3022 may be ionimplanted for Vt control and/or body bias efficiency. An optical step,such as illustrated by exemplary STI ray 3067, may be performed toanneal etch damage and densify the STI oxide in transistor and backchannel isolation regions 3005. The doping concentration of channelregion 3023 may include vertical or horizontal gradients ofconcentration or layers of differing doping concentrations. The dopingconcentration of back-channel region 3022 may include vertical orhorizontal gradients of concentration or layers of differing dopingconcentrations. Any additional doping, such as ion-implanted channelimplants, may be activated and annealed with optical annealing, such asillustrated by exemplary implant ray 3069, as described herein. Theoptical anneal, such as exemplary STI ray 3067, and/or exemplary implantray 3069 may be performed at separate times and processing parameters(such as laser energy, frequency, etc.) or may be done in combination oras one optical anneal. Optical absorber and or reflective layers orregions may be employed to enhance the anneal and/or protect theunderlying sensitive structures. Moreover, multiple pulses of the lasermay be utilized to improve the anneal, activation, and yield of theprocess. BOX region 3031 may be a relatively thin dielectric, includingthe thickness range of 5 nm to 100 nm, at least a portion of which beingbetween the back-channel region 3022 and channel region 3023.Back-channel region 3022 could be constructed from a material that wouldnot be damaged by the optical anneal process. Such could be a refractorymetal or doped silicon in crystallized form, poly or amorphous, or otherconductive material that are acceptable for semiconductor processing andcan withstand high temperature of 700° C. or higher.

As illustrated in FIG. 30E, a transistor forming process, such as aconventional HKMG with raised source and drains (S/D), may be performed.For example, a dummy gate stack (not shown), utilizing oxide andpolysilicon, may be formed, gate spacers 3030 may be formed, raised S/Dregions 3032 and channel stressors may be formed by etch and epitaxialdeposition, for example, of SiGe and/or SiC depending on P or N channel(and may be doped in-situ or ion-implantation and optical annealactivation), LDD and S/D ion-implantations may be performed, and firstILD 3036 may be deposited and CMP'd to expose the tops of the dummygates. Thus transistor channel region 3033 and S/D & LDD regions 3035may be formed. The dummy gate stack may be removed and a gate dielectric3007 may be formed and a gate metal material gate electrode 3008,including a layer of proper work function metal (Ti_(x)Al_(y),N_(z) forexample) and a conductive fill, such as aluminum, and may be depositedand CMP'd. The gate dielectric 3007 may be an atomic layer deposited(ALD) gate dielectric that may be paired with a work function specificgate metal in the industry standard high k metal gate process schemes,for example, as described in the incorporated references. Alternatively,the gate dielectric 3007 may be formed with a low temperature processesincluding, for example, LPCVD SiO₂ oxide deposition (see Ahn, J., etal., “High-quality MOSFET's with ultrathin LPCVD gate SiO2,” IEEEElectron Device Lett., vol. 13, no. 4, pp. 186-188, April 1992) or lowtemperature microwave plasma oxidation of the silicon surfaces (see Kim,J. Y., et al., “The excellent scalability of the RCAT(recess-channel-array-transistor) technology for sub-70 nm DRAM featuresize and beyond,” 2005 IEEE VLSI-TSA International Symposium, pp. 33-30,25-27 Apr. 2005) and a gate material with proper work function and lessthan approximately 400° C. deposition temperature such as, for example,tungsten or aluminum may be deposited. An optical step, such asrepresented by exemplary anneal ray 3021, may be performed to densifyand/or remove defects from gate dielectric 3007, anneal defects andactivate dopants such as LDD and S/D implants, densify the first ILD3036, form DSS junctions (Dopant Segregated Schottky such as NiSi₂),and/or form contact and S/D silicides (not shown). The optical annealmay be performed at each sub-step as desired, or may be done at prior tothe HKMG deposition (such as after the dummy gate but before the HKMGformation), or various combinations. Optionally, portions of transistorisolation region 3086 and BOX region 3031 may be lithographicallydefined and etched away, thus forming second transistor isolationregions 3076 and PD transistor area 3068. Partially depleted transistors(not shown) may be constructed in a similar manner as the FD-MOSFETsconstructed on transistor channel region 3033 herein, but now with thethicker back-channel region 3022 silicon as its channel body. PDtransistor area 3068 may also be utilized to later form a directconnection thru a contact to the back-channel region 3022 for back biasand Vt control of the transistor with transistor channel region 3033. Ifno PD devices are desired, then it may be more efficient to later form adirect connection thru a contact to the back-channel region 3022 forback bias and Vt control of the transistor with transistor channelregion 3033 by etching a contact thru transistor isolation region 3086.Raised S/D regions 3032 may be formed by low temperature (less than 400°C.) deposition of in-situ doped polysilicon or amorphous silicon intothe S/D openings, an optical anneal to further crystallize and dopantactivate the raised S/D material, and removal of excess raised S/Dmaterial.

As illustrated in FIG. 30F, a low temperature thick oxide 3009 may bedeposited and planarized. Source, gate, drain, two types of back contactopenings may be masked, etched, and filled with electrically conductivematerials preparing the transistors to be connected via metallization.Thus gate contact 3011 connects to gate electrode 3008, source & draincontacts 3040 connect to raised S/D regions 3032, back channel contact3044 may connect to back-channel region 3022, and direct back contact3045 may connect to back-channel region 3022. An optical step, such asillustrated by exemplary ILD anneal ray 3051, may be performed to annealcontact etch damage and densify the thick oxide 3009. Back channelcontact 3044 and direct back contact 3045 may be formed to connect toshield/heat sink layer 3088 by further etching, and may be useful forhard wiring a back bias that may be controlled by, for example, thesecond layer or first layer circuitry into the FD MOSFET.

As illustrated in FIG. 30G, thru layer vias (TLVs) 3060 may be formed byetching thick oxide 3009, first ILD 3036, transistor and back channelisolation regions 3005, oxide layer 3080, into a portion of the upperoxide layer BEOL isolation 3096 of acceptor wafer 3010 BEOL, and fillingwith an electrically and thermally conducting material (such as tungstenor cooper) or an electrically non-conducting but thermally conductingmaterial (such as described elsewhere within). Second device layer metalinterconnect 3061 may be formed by conventional processing. TLVs 3060may be constructed of thermally conductive but not electricallyconductive materials, for example, DLC (Diamond Like Carbon), and mayconnect the FD-MOSFET transistor device and other devices on the top(second) crystalline layer thermally to shield/heat sink layer 3088.TLVs 3060 may be constructed out of electrically and thermallyconductive materials, such as Tungsten, Copper, or aluminum, and mayprovide a thermal and electrical connection path from the FD-MOSFETtransistor device and other devices on the top (second) crystallinelayer to shield/heat sink layer 3088, which may be a ground or Vdd planein the design/layout. TLVs 3060 may be also constructed in the devicescribelanes (pre-designed in base layers or potential dicelines) toprovide thermal conduction to the heat sink, and may be sawed/diced offwhen the wafer is diced for packaging not shown). Shield/heat sink layer3088 may be configured to act (or adapted to act) as an emf(electro-motive force) shield to prevent direct layer to layercross-talk between transistors in the donor wafer layer and transistorsin the acceptor wafer. In addition to static ground or Vdd biasing,shield/heat sink layer 3088 may be actively biased with ananti-interference signal from circuitry residing on, for example, alayer of the 3D-IC or off chip. The formed FD-MOSFET transistor devicemay include semiconductor regions wherein the dopant concentration ofneighboring regions of the transistor in the horizontal plane, such astraversed by exemplary dopant plane 3034, may have regions, for example,transistor channel region 3033 and S/D & LDD regions 3035, that differsubstantially in dopant concentration, for example, a 10 times greaterdoping concentration in S/D & LDD regions 3035 than in transistorchannel region 3033, and/or may have a different dopant type, such as,for example p-type or n-type dopant, and/or may be doped andsubstantially undoped in the neighboring regions. For example,transistor channel region 3033 may be very lightly doped (less than 1e15atoms/cm³) or nominally un-doped (less than 1e14 atoms/cm³) and S/D &LDD regions 3035 may be doped at greater than 1e15 atoms/cm³ or greaterthan 1e16 atoms/cm³. For example, transistor channel region 3033 may bedoped with p-type dopant and S/D & LDD regions 3035 may be doped withn-type dopant.

A thermal conduction path may be constructed from the devices in theupper layer, the transferred donor layer and formed transistors, to theacceptor wafer substrate and associated heat sink. The thermalconduction path from the FD-MOSFET transistor device and other deviceson the top (second) crystalline layer, for example, raised S/D regions3032, to the acceptor wafer heat sink 3097 may include source & draincontacts 3040, second device layer metal interconnect 3061, TLV 3060,shield path connect 3085 (shown as twice), shield path via 3083 (shownas twice), metal interconnect 3081, first (acceptor) layer metalinterconnect 3091, acceptor wafer transistors and devices 3093, andacceptor substrate 3095. The elements of the thermal conduction path mayinclude materials that have a thermal conductivity greater than 10W/m-K, for example, copper (about 400 W/m-K), aluminum (about 237W/m-K), and Tungsten (about 173 W/m-K), and may include material withthermal conductivity lower than 10 W/m-K but have a high heat transfercapacity due to the wide area available for heat transfer and thicknessof the structure (Fourier's Law), such as, for example, acceptorsubstrate 3095. The elements of the thermal conduction path may includematerials that are thermally conductive but may not be substantiallyelectrically conductive, for example, Plasma Enhanced Chemical VaporDeposited Diamond Like Carbon-PECVD DLC (about 1000 W/m-K), and ChemicalVapor Deposited (CVD) graphene (about 5000 W/m-K). The acceptor waferinterconnects may be substantially surrounded by BEOL isolation 3096,which may be a dielectric such as, for example, carbon doped siliconoxides. The heat removal apparatus, which may include acceptor waferheat sink 3097, may include an external surface from which heat transfermay take place by methods such as air cooling, liquid cooling, orattachment to another heat sink or heat spreader structure.

Furthermore, some or all of the layers utilized as shield/heat sinklayer 3088, which may include shapes of material such as the strips orfingers as illustrated in FIG. 27B-1 , may be driven by a portion of thesecond layer transistors and circuits (within the transferred donorwafer layer or layers) or the acceptor wafer transistors and circuits,to provide a programmable back-bias to at least a portion of the secondlayer transistors. The programmable back bias may utilize a circuit todo so, for example, such as shown in FIG. 17B of U.S. Pat. No.8,273,610, the contents incorporated herein by reference; wherein the‘Primary’ layer may be the second layer of transistors for which theback-bias is being provided, the ‘Foundation’ layer could be either thesecond layer transistors (donor) or first layer transistors (acceptor),and the routing metal lines connections 1723 and 1724 may includeportions of the shield/heat sink layer 3088 layer or layers. Moreover,some or all of the layers utilized as shield/heat sink layer 3088, whichmay include strips or fingers as illustrated in FIG. 27B-1 , may bedriven by a portion of the second layer transistors and circuits (withinthe transferred donor wafer layer or layers) or the acceptor wafertransistors and circuits to provide a programmable power supply to atleast a portion of the second layer transistors. The programmable powersupply may utilize a circuit to do so, for example, such as shown inFIG. 17C of U.S. Pat. No. 8,273,610, the contents incorporated herein byreference; wherein the ‘Primary’ layer may be the second layer oftransistors for which the programmable power supplies are being providedto, the ‘Foundation’ layer could be either the second layer transistors(donor) or first layer transistors (acceptor), and the routing metalline connections from Vout to the various second layer transistors mayinclude portions of the shield/heat sink layer 3088 layer or layers. TheVsupply on line 17C12 and the control signals on control line 17C16 maybe controlled by and/or generated in the second layer transistors (forexample donor wafer device structures such as the FD-MOSFETs formed asdescribed in relation to FIG. 30 ) or first layer transistors (acceptor,for example acceptor wafer transistors and devices 3093), or off chipcircuits. Furthermore, some or all of the layers utilized as shield/heatsink layer 3088, which may include strips or fingers as illustrated inFIG. 27B-1 or other shapes such as those in FIG. 27B, may be utilized todistribute independent power supplies to various portions of the secondlayer transistors (for example donor wafer device structures such as theFD-MOSFETs formed as described in relation to FIG. 30 ) or first layertransistors (acceptor, for example acceptor wafer transistors anddevices 3093) and circuits; for example, one power supply and/or voltagemay be routed to the sequential logic circuits of the second layer and adifferent power supply and/or voltage routed to the combinatorial logiccircuits of the second layer. Moreover, the power distributioncircuits/grid may be designed so that Vdd may have a different value foreach stack layer. Patterning of shield/heat sink layer 3088 or layerscan impact their heat-shielding capacity. This impact may be mitigated,for example, by enhancing the top shield/heat sink layer 3088 arealdensity, creating more of the secondary shield/heat sink layers 3088, orattending to special CAD rules regarding their metal density, similar toCAD rules that are required to accommodate Chemical-MechanicalPlanarization (CMP). These constraints would be integrated into a designand layout EDA tool. Moreover, the second layer of circuits andtransistors, for example, for example donor wafer device structures suchas the FD-MOSFETs formed as described in relation to FIG. 30 , mayinclude I/O logic devices, such as SerDes (Serialiser/Deserialiser), andconductive bond pads (not shown) (herein such as FIG. 33 ). The outputor input conductive pads of the I/O circuits may be coupled, for exampleby bonded wires, to external devices. The output or input conductivepads may also act as a contact port for the 3D device output to connectto external devices. The emf generated by the I/O circuits could beshielded from the other layers in the stack by use of, for example, theshield/heat sink layer 3088. Placement of the I/O circuits on the samestack layer as the conductive bond pad may enable close coupling of thedesired I/O energy and lower signal loss. Furthermore, the second layerof circuits and transistors, for example donor wafer device structuressuch as the FD-MOSFETs formed as described in relation to FIG. 30 , mayinclude RF (Radio Frequency) circuits and/or at least one antenna. Forexample, the second layer of circuits and transistors may include RFcircuits to enable an off-chip communication capability to externaldevices, for example, a wireless communication circuit or circuits suchas a Bluetooth protocol or capacitive coupling. The emf generated by theRF circuits could be shielded from the other layers in the stack by useof, for example, the shield/heat sink layer 3088.

TLVs 3060 may be formed through the transferred layers. As thetransferred layers may be thin, on the order of about 200 nm or less inthickness, the TLVs may be easily manufactured as a typical metal tometal via may be, and said TLV may have state of the art diameters suchas nanometers or tens to a few hundreds of nanometers, such as, forexample about 150 nm or about 100 nm or about 50 nm. The thinner thetransferred layers, the smaller the thru layer via diameter obtainable,which may result from maintaining manufacturable via aspect ratios. Thethickness of the layer or layers transferred according to someembodiments of the invention may be designed as such to match and enablethe most suitable obtainable lithographic resolution (and enable the useof conventional state of the art lithographic tools), such as, forexample, less than about 10 nm, 14 nm, 22 nm or 28 nm linewidthresolution and alignment capability, such as, for example, less thanabout 5 nm, 10 nm, 20 nm, or 40 nm alignment accuracy/precision/error,of the manufacturing process employed to create the thru layer vias orany other structures on the transferred layer or layers.

Formation of CMOS in one transferred layer and the orthogonal connectstrip methodology may be found as illustrated in at least FIGS. 30-33,73-80, and 94 and related specification sections of U.S. Pat. No.8,273,610, and may be applied to at least the FIG. 30 formationtechniques herein. Transferred layer or layers may have regions of STIor other transistor elements within it or on it when transferred, butwould then use alignment and connection schemes for layer transfer ofpatterned layers as described in incorporated patent references.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 30A through 30G are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations are possible such as, for example, a p-channel FD-MOSFET maybe formed with changing the types of dopings appropriately. Moreover,the SOI donor wafer substrate 3000 may be n type or un-doped.Furthermore, transistor and back channel isolation regions 3005 andtransistor isolation region 3086 may be formed by a hard mask definedprocess flow, wherein a hard mask stack, such as, for example, siliconoxide and silicon nitride layers, or silicon oxide and amorphous carbonlayers, may be utilized. Moreover, CMOS FD MOSFETs may be constructedwith n-MOSFETs in a first mono-crystalline silicon layer and p-MOSFETsin a second mono-crystalline layer, which may include differentcrystalline orientations of the mono-crystalline silicon layers, such asfor example, <100>, <111> or <551>, and may include different contactsilicides for optimum contact resistance to p or n type source, drains,and gates. Further, dopant segregation techniques (DST) may be utilizedto efficiently modulate the source and drain Schottky barrier height forboth p and n type junctions formed. Furthermore, raised source and draincontact structures, such as etch and epi SiGe and SiC, may be utilizedfor strain and contact resistance improvements and the damage from theprocesses may be optically annealed. Many other modifications within thescope of the invention will suggest themselves to such skilled personsafter reading this specification. Thus the invention is to be limitedonly by the appended claims.

A planar n-channel JFET or JLT with an optional integrated heatshield/spreader suitable for a monolithic 3D IC may be constructed asfollows. Being bulk conduction devices rather than surface conductiondevices, the MET and JLT may provide an improved transistor variabilitycontrol and conduction channel electrostatic control. Sub-thresholdslope, DIBL, and other short channel effects are greatly improved due tothe firm gate electrostatic control over the channel. Moreover, a heatspreading, heat conducting and/or optically reflecting material layer orlayers may be incorporated between the sensitive metal interconnectlayers and the layer or regions being optically irradiated and annealedto repair defects in the crystalline 3D-IC layers and regions and toactivate semiconductor dopants in the crystalline layers or regions of a3D-IC without harm to the sensitive metal interconnect and associateddielectrics. Furthermore, a buried doped layer and channel dopantshaping, even to an un-doped channel, may allow for efficient adaptiveand dynamic body biasing to control the transistor threshold andthreshold variations, the concepts shown in FIG. 26 herein may beapplied to the MET. As well, the back plane and body bias tap conceptsshown in FIG. 30 herein may be utilized for the JFET and JLT devices. Asone of ordinary skill in the art would understand, many other types oftransistors, such as a FinFet transistor, could be made utilizingsimilar concepts in their construction. FIG. 31A-G illustrates anexemplary n-channel JFET which may be constructed in a 3D stacked layerusing procedures outlined below and in U.S. Pat. Nos. 8,273,610,9,099,526, 9,219,005, 8,557,632 and 8,581,349. The contents of theforegoing applications are incorporated herein by reference.

As illustrated in FIG. 31A, an N− substrate donor wafer 3100 may beprocessed to include a wafer sized layer of doping across the wafer, N−doped layer 3102. The N− doped layer 3102 may be formed by ionimplantation and thermal anneal. N− substrate donor wafer 3100 mayinclude a crystalline material, for example, mono-crystalline (singlecrystal) silicon. N− doped layer 3102 may be very lightly doped (lessthan 1e15 atoms/cm³) or lightly doped (less than 1e16 atoms/cm³) ornominally un-doped (less than 1e14 atoms/cm³). N− doped layer 3102 mayhave additional ion implantation and anneal processing to provide adifferent dopant level than N− substrate donor wafer 3100 and may havegraded or various layers of doping concentration. The layer stack mayalternatively be formed by epitaxially deposited doped or undopedsilicon layers, or by a combination of epitaxy and implantation, or bylayer transfer. Annealing of implants and doping may include, forexample, conductive/inductive thermal, optical annealing techniques ortypes of Rapid Thermal Anneal (RTA or spike).

As illustrated in FIG. 31B, the top surface of N− substrate donor wafer3100 layer stack may be prepared for oxide wafer bonding with adeposition of an oxide or by thermal oxidation of N− doped layer 3102 toform oxide layer 3180. A layer transfer demarcation plane (shown asdashed line) 3199 may be formed by hydrogen implantation or othermethods as described in the incorporated references. The N− substratedonor wafer 3100, such as surface 3182, and acceptor wafer 3110 may beprepared for wafer bonding as previously described and low temperature(less than approximately 400° C.) bonded. Acceptor wafer 3110, asdescribed in the incorporated references, may include, for example,transistors, circuitry, and metal, such as, for example, aluminum orcopper, interconnect wiring, a metal shield/heat sink layer or layers,and thru layer via metal interconnect strips or pads. Acceptor wafer3110 may be substantially comprised of a crystalline material, forexample mono-crystalline silicon or germanium, or may be an engineeredsubstrate/wafer such as, for example, an SOI (Silicon on Insulator)wafer or GeOI (Germanium on Insulator) substrate. Acceptor wafer 3110may include transistors such as, for example, MOSFETS, FD-MOSFETS,FinFets, FD-RCATs, BJTs, HEMTs, and/or HBTs. The portion of the N− dopedlayer 3102 and the N− substrate donor wafer 3100 that may be above (whenthe layer stack is flipped over and bonded to the acceptor wafer 3110)the layer transfer demarcation plane 3199 may be removed by cleaving orother low temperature processes as described in the incorporatedreferences, such as, for example, ion-cut with mechanical or thermalcleave or other layer transfer methods, thus forming remaining N− layer3103. Damage/defects to crystalline structure of N− doped layer 3102 maybe annealed by some of the annealing methods described herein, forexample the short wavelength pulsed laser techniques, wherein the N−doped layer 3102 may be heated to defect annealing temperatures, but thelayer transfer demarcation plane 3199 may be kept below the temperatefor cleaving and/or significant hydrogen diffusion. The optical energymay be deposited in the upper layer of the stack, for example nearsurface 3182, and annealing of the N− doped layer 3102 may take placevia heat diffusion. Moreover, multiple pulses of the laser may beutilized to improve the anneal, activation, and yield of the process.

As illustrated in FIG. 31C, oxide layer 3180 and remaining N− layer 3103have been layer transferred to acceptor wafer 3110. The top surface ofremaining N− layer 3103 may be chemically or mechanically polished,and/or may be thinned by low temperature oxidation and strip processes,such as the TEL SPA tool radical oxidation and HF:H₂O solutions asdescribed herein and in referenced patents and patent applications. Thruthe processing, the wafer sized layer remaining N− layer 3103 could bethinned from its original total thickness, and its final total thicknesscould be in the range of about 3 nm to about 30 nm, for example, 3 nm, 5nm, 7 nm, 10 nm, 150 nm, 20 nm, or 30 nm. Remaining N− layer 3103 mayhave a thickness that may allow full gate control of channel operationwhen the JFET (or JLT) transistor is substantially completely formed.Acceptor wafer 3110 may include one or more (two are shown in thisexample) shield/heat sink layers 3188, which may include materials suchas, for example, Aluminum, Tungsten (a refractory metal), Copper,silicon or cobalt based silicides, or forms of carbon such as carbonnanotubes, and may be layered itself as described in FIG. 50 ofincorporated patent reference U.S. Pat. No. 9,385,058. Each shield/heatsink layer 3188 may have a thickness range of about 50 nm to about 1 mm,for example, 50 nm, 100 nm, 200 nm, 300 nm, 500 nm, 0.1 um, 1 um, 2 um,and 10 um. Shield/heat sink layer 3188 may include isolation openings3187, and alignment mark openings (not shown), which may be utilized forshort wavelength alignment of top layer (donor) processing to theacceptor wafer alignment marks (not shown). Shield/heat sink layer 3188may include one or more shield path connects 3185 and shield path vias3183. Shield path via 3183 may thermally and/or electrically couple andconnect shield path connect 3185 to acceptor wafer 3110 interconnectmetallization layers such as, for example, exemplary acceptor metalinterconnect 3181 (shown). Shield path connect 3185 may also thermallyand/or electrically couple and connect each shield/heat sink layer 3188to the other and to acceptor wafer 3110 interconnect metallizationlayers such as, for example, acceptor metal interconnect 3181, therebycreating a heat conduction path from the shield/heat sink layer 3188 tothe acceptor substrate 3195, and a heat sink (shown in FIG. 31G).Isolation openings 3187 may include dielectric materials, similar tothose of BEOL isolation 3196. Acceptor wafer 3110 may include first(acceptor) layer metal interconnect 3191, acceptor wafer transistors anddevices 3193, and acceptor substrate 3195. Various topside defectanneals may be utilized. For this illustration, an optical beam such asthe laser annealing previously described is used. Optical anneal beamsmay be optimized to focus light absorption and heat generation within orat the surface of remaining N− layer 3103 and provide surface smoothingand/or defect annealing (defects may be from the cleave and/or theion-cut implantation) with exemplary smoothing/annealing ray 3166. Thelaser assisted smoothing/annealing with the absorbed heat generated byexemplary smoothing/annealing ray 3166 may also include a pre-heat ofthe bonded stack to, for example, about 100° C. to about 400° C., and/ora rapid thermal spike to temperatures above about 200° C. to about 600°C. Additionally, absorber layers or regions, for example, includingamorphous carbon, amorphous silicon, and phase changing materials (seeU.S. Pat. Nos. 6,635,588 and 6,319,821 to Hawryluk et al. for example),may be utilized to increase the efficiency of the optical energy capturein conversion to heat for the desired annealing or activation processes.Moreover, multiple pulses of the laser may be utilized to improve theanneal, activation, and yield of the process. Reflected ray 3163 may bereflected and/or absorbed by shield/heat sink layer 3188 regions thusblocking the optical absorption of ray blocked metal interconnect 3181.Annealing of dopants or annealing of damage in remaining N− layer 3103,such as from the H cleave implant damage, may be also accomplished by aset of rays such as repair ray 3165. Heat generated by absorbed photonsfrom, for example, smoothing/annealing ray 3166, reflected ray 3163,and/or repair ray 3165 may also be absorbed by shield/heat sink layer3188 regions and dissipated laterally and may keep the temperature ofunderlying metal layers, such as metal interconnect 3181, and othermetal layers below it, cooler and prevent damage. Shield/heat sink layer3188 and associated dielectrics may laterally spread and conduct theheat generated by the topside defect anneal, and in conjunction with thedielectric materials (low heat conductivity) above and below shield/heatsink layer 3188, keep the interconnect metals and low-k dielectrics ofthe acceptor wafer interconnect layers cooler than a damage temperature,such as, for example, 400° C. A second layer of shield/heat sink layer3188 may be constructed (shown) with a low heat conductive materialsandwiched between the two heat sink layers, such as silicon oxide orcarbon doped ‘low-k’ silicon oxides, for improved thermal protection ofthe acceptor wafer interconnect layers, metal and dielectrics.Shield/heat sink layer 3188 may act as a heat spreader. Electricallyconductive materials may be used for the two layers of shield/heat sinklayer 3188 and thus may provide, for example, a Vss and a Vdd planeand/or grid that may be connected to the donor layer transistors above,as well may be connected to the acceptor wafer transistors below, and/ormay provide below transferred layer device interconnection. Noise on thepower grids, such as the Vss and Vdd plane power conducting lines/wires,may be mitigated by attaching/connecting decoupling capacitors onto thepower conducting lines of the grids. The decoupling caps, which may bewithin the second layer (donor, for example, donor wafer devicestructures) or first layer (acceptor, for example acceptor wafertransistors and devices 3193), may include, for example, trenchcapacitors such as described by Pei, C., et al., “A novel, low-cost deeptrench decoupling capacitor for high-performance, low-power bulk CMOSapplications,” ICSICT (9^(th) International Conference on Solid-Stateand Integrated-Circuit Technology) 2008, October 2008, pp. 1146-1149, ofIBM. The decoupling capacitors may include, for example, planarcapacitors, such as poly to substrate or poly to poly, or MiM capacitors(Metal-Insulator-Metal). Shield/heat sink layer 3188 may includematerials with a high thermal conductivity greater than 10 W/m-K, forexample, copper (about 400 W/m-K), aluminum (about 237 W/m-K), Tungsten(about 173 W/m-K), Plasma Enhanced Chemical Vapor Deposited Diamond LikeCarbon-PECVD DLC (about 1000 W/m-K), and Chemical Vapor Deposited (CVD)graphene (about 5000 W/m-K). Shield/heat sink layer 3188 may besandwiched and/or substantially enclosed by materials with a low thermalconductivity (less than 10 W/m-K), for example, silicon dioxide (about1.4 W/m-K). The sandwiching of high and low thermal conductivitymaterials in layers, such as shield/heat sink layer 3188 and under &overlying dielectric layers, spreads the localized heat/light energy ofthe topside anneal laterally and protects the underlying layers ofinterconnect metallization & dielectrics, such as in the acceptor wafer3110, from harmful temperatures or damage. When there may be more thanone shield/heat sink layer 3188 in the device, the heat conducting layerclosest to the second crystalline layer or oxide layer 3180 may beconstructed with a different material, for example a high melting pointmaterial, for example a refractory metal such as tungsten, than theother heat conducting layer or layers, which may be constructed with,for example, a lower melting point material, for example such asaluminum or copper. Now transistors may be formed with low effectivetemperature (less than approximately 400° C. exposure to the acceptorwafer 3110 sensitive layers, such as interconnect and device layers)processing, and may be aligned to the acceptor wafer alignment marks(not shown) as described in the incorporated references. This mayinclude further optical defect annealing or dopant activation steps. TheN− donor wafer 3100 may now also be processed, such as smoothing andannealing, and reused for additional layer transfers. The insulatorlayer, such as deposited bonding oxides (for example oxide layer 3180)and/or before bonding preparation existing oxides (for example the BEOLisolation 3196 on top of the topmost metal layer of shield/heat sinklayer 3188), between the donor wafer transferred monocrystalline layerand the acceptor wafer topmost metal layer, may include thicknesses ofless than 1 um, less than 500 nm, less than 400 nm, less than 300 nm,less than 200 nm, or less than 100 nm.

As illustrated in FIG. 31D, transistor isolation regions 3105 may beformed by mask defining and plasma/RIE etching remaining N− layer 3102substantially to the top of oxide layer 3180 (not shown), substantiallyinto oxide layer 3180, or into a portion of the upper oxide layer ofacceptor wafer 3110 (not shown). Thus N− channel region 3123 may beformed. A low-temperature gap fill dielectric, such as SACVD oxide, maybe deposited and chemically mechanically polished, the oxide remainingin isolation regions 3105. An optical step, such as illustrated byexemplary STI ray 3167, may be performed to anneal etch damage anddensify the STI oxide in isolation regions 3105. The dopingconcentration of N− channel region 3123 may include gradients ofconcentration or layers of differing doping concentrations. Anyadditional doping, such as ion-implanted channel implants, may beactivated and annealed with optical annealing, such as illustrated byexemplary implant ray 3169, as described herein. The optical anneal,such as exemplary STI ray 3167, and/or exemplary implant ray 3169 may beperformed at separate times and processing parameters (such as laserenergy, frequency, etc.) or may be done in combination or as one opticalanneal. Optical absorber and or reflective layers or regions may beemployed to enhance the anneal and/or protect the underlying sensitivestructures. Moreover, multiple pulses of the laser may be utilized toimprove the anneal, activation, and yield of the process.

As illustrated in FIG. 31E, a JFET transistor forming process withraised source and drains (S/D), may be performed. For example, a shallowP+ region 3177 may be performed to create a JFET gate by utilizing amask defined implant of P+ type dopant, such as, for example, Boron. Alaser or other method of optical annealing may be utilized to activatethe P+ implanted dopant. Alternatively, a directly in contact with thesilicon channel P+ doped poly gate may be formed, with appropriateisolation from the source and drains, and dopant from that gate may alsobe utilized to form shallow P+ region 3177, for example, by diffusionfrom an optical anneal. S/D ion-implantations may be performed and laserannealed to create N+ regions 3135, and thus forming N− channel region3133. The N+ regions 3135 may have a doping concentration that may bemore than 10× the doping concentration of N− channel region 3133. FirstILD 3136 may be deposited and CMP'd, and then openings may be etched toenable formation of gate 3178 and raised S/D regions 3132. Raised S/Dregions 3132 and channel stressors may be formed by etch and epitaxialdeposition, for example, of SiGe and/or SiC depending on P or N channel,and may be doped in-situ or ion-implantation and optical annealactivation. Gate 3178 may be formed with a metal to enable an optimalSchottky contact, for example aluminum, or may make an electricalconnection to shallow P+ region 3177. An optical step, such asrepresented by exemplary anneal ray 3121, may be performed to densifyand/or remove defects from gate 3178 and its connection to shallow P+region 3177, anneal defects and activate dopants such as S/D and otherburied channel tailoring implants, densify the first ILD 3136, form DSSjunctions (Dopant Segregated Schottky such as NiSi₂), and/or formcontact and S/D silicides (not shown). The optical anneal may beperformed at each sub-step as desired, or may be done at prior toSchottky metal deposition, or various combinations. Moreover, multiplepulses of the laser may be utilized to improve the anneal, activation,and yield of the process. Raised S/D regions 3132 may be formed by lowtemperature (less than 400° C.) deposition of in-situ doped polysiliconor amorphous silicon into the S/D openings, an optical anneal to furthercrystallize and dopant activate the raised S/D material, and removal ofexcess raised S/D material.

As illustrated in FIG. 31E-1 , an alternate transistor forming processto form a JLT with a conventional HKMG with raised source and drains(S/D), may be performed. For example, a dummy gate stack (not shown),utilizing oxide and polysilicon, may be formed, gate spacers 3130 may beformed, raised S/D regions 3132 and channel stressors may be formed byetch and epitaxial deposition, for example, of SiGe and/or SiC dependingon P or N channel (and may be doped in-situ or ion-implantation andoptical anneal activation), LDD and N++ S/D ion-implantations may beperformed, and first ILD 3136 may be deposited and CMP'd to expose thetops of the dummy gates. Thus JLT transistor channel 3133-1 and N++ S/D& LDD regions 3135-1 may be formed. N− doped layer in FIG. 31A may bedoped to N+, concentrations in excess of 1×10¹⁹ atms/cm³, to enable aconductive JLT channel (JLT transistor channel 3133-1) and has beendescribed elsewhere in referenced patents and patent applications. JLTtransistor channel 3133-1 may also be doped by implantation after thelayer transfer, and activated/annealed with optical techniques. Thedummy gate stack may be removed and a gate dielectric 3107 may be formedand a gate metal material gate electrode 3108, including a layer ofproper work function metal to enable channel cut-off at 0 gate bias(described in referenced U.S. Pat. No. 8,273,610) and a conductive fill,such as aluminum, and may be deposited and CMP'd. The gate dielectric3107 may be an atomic layer deposited (ALD) gate dielectric that may bepaired with a work function specific gate metal in the industry standardhigh k metal gate process schemes, for example, as described in theincorporated references. Alternatively, the gate dielectric 3107 may beformed with a low temperature processes including, for example, LPCVDSiO₂ oxide deposition (see Ahn, J., et al., “High-quality MOSFET's withultrathin LPCVD gate SiO2,” IEEE Electron Device Lett., vol. 13, no. 4,pp. 186-188, April 1992) or low temperature microwave plasma oxidationof the silicon surfaces (see Kim, J. Y., et al., “The excellentscalability of the RCAT (recess-channel-array-transistor) technology forsub-70 nm DRAM feature size and beyond,” 2005 IEEE VLSI-TSAInternational Symposium, pp. 33-31, 25-27 Apr. 2005) and a gate materialwith proper work function and less than approximately 400° C. depositiontemperature such as, for example, tungsten or aluminum may be deposited.An optical step, such as represented by exemplary anneal ray 3121, maybe performed to densify and/or remove defects from gate dielectric 3107,anneal defects and activate dopants such as N+ channel, LDD and N++ S/Dimplants, densify the first ILD 3136, form DSS junctions (DopantSegregated Schottky such as NiSi₂), and/or form contact and S/Dsilicides (not shown). The optical anneal may be performed at eachsub-step as desired, or may be done at prior to the HKMG deposition(such as after the dummy gate but before the HKMG formation), or variouscombinations. Raised S/D regions 3132 may be formed by low temperature(less than 400° C.) deposition of in-situ doped polysilicon or amorphoussilicon into the S/D openings, an optical anneal to further crystallizeand dopant activate the raised S/D material, and removal of excessraised S/D material. The following steps may be applied to the JFET orJLT flows.

As illustrated in FIG. 31F, a low temperature thick oxide 3109 may bedeposited and planarized. Source, gate, and drain contacts openings maybe masked and etched preparing the transistors to be connected viametallization. Thus gate contact 3111 connects to gate 3178, and source& drain contacts 3140 connect to raised S/D regions 3132. An opticalstep, such as illustrated by exemplary ILD anneal ray 3151, may beperformed to anneal contact etch damage and densify the thick oxide3109.

As illustrated in FIG. 31G, thru layer vias (TLVs) 3160 may be formed byetching thick oxide 3109, first ILD 3136, isolation regions 3105, oxidelayer 3180, into a portion of the upper oxide layer BEOL isolation 3196of acceptor wafer 3110 BEOL, and filling with an electrically andthermally conducting material (such as tungsten or cooper) or anelectrically non-conducting but thermally conducting material (such asdescribed elsewhere within). Second device layer metal interconnect 3161may be formed by conventional processing. TLVs 3160 may be constructedof thermally conductive but not electrically conductive materials, forexample, DLC (Diamond Like Carbon), and may connect the JFET or JLTtransistor device and other devices on the top (second) crystallinelayer thermally to shield/heat sink layer 3188. TLVs 3160 may beconstructed out of electrically and thermally conductive materials, suchas Tungsten, Copper, or aluminum, and may provide a thermal andelectrical connection path from the JFET or JLT transistor device andother devices on the top (second) crystalline layer to shield/heat sinklayer 3188, which may be a ground or Vdd plane in the design/layout.TLVs 3160 may be also constructed in the device scribelanes(pre-designed in base layers or potential dicelines) to provide thermalconduction to the heat sink, and may be sawed/diced off when the waferis diced for packaging not shown). Shield/heat sink layer 3188 may beconfigured to act (or adapted to act) as an emf (electro-motive force)shield to prevent direct layer to layer cross-talk between transistorsin the donor wafer layer and transistors in the acceptor wafer. Inaddition to static ground or Vdd biasing, shield/heat sink layer 3188may be actively biased with an anti-interference signal from circuitryresiding on, for example, a layer of the 3D-IC or off chip. The formedJFET (or JLT) transistor device may include semiconductor regionswherein the dopant concentration of neighboring regions of thetransistor in the horizontal plane, such as traversed by exemplarydopant plane 3134, may have regions, for example, N− channel region 3133and S/D N+ regions 3135, that differ substantially in dopantconcentration, for example, a 10 times greater doping concentration inN+ regions 3135 than in N− channel region 3133, and/or may be doped andsubstantially undoped in the neighboring regions.

A thermal conduction path may be constructed from the devices in theupper layer, the transferred donor layer and formed transistors, to theacceptor wafer substrate and associated heat sink. The thermalconduction path from the MET or JLT transistor device and other deviceson the top (second) crystalline layer, for example, raised S/D regions3132, to the acceptor wafer heat sink 3197 may include source & draincontacts 3140, second device layer metal interconnect 3161, TLV 3160,shield path connect 3185 (shown as twice), shield path via 3183 (shownas twice), metal interconnect 3181, first (acceptor) layer metalinterconnect 3191, acceptor wafer transistors and devices 3193, andacceptor substrate 3195. The elements of the thermal conduction path mayinclude materials that have a thermal conductivity greater than 10W/m-K, for example, copper (about 400 W/m-K), aluminum (about 237W/m-K), and Tungsten (about 173 W/m-K), and may include material withthermal conductivity lower than 10 W/m-K but have a high heat transfercapacity due to the wide area available for heat transfer and thicknessof the structure (Fourier's Law), such as, for example, acceptorsubstrate 3195. The elements of the thermal conduction path may includematerials that are thermally conductive but may not be substantiallyelectrically conductive, for example, Plasma Enhanced Chemical VaporDeposited Diamond Like Carbon-PECVD DLC (about 1000 W/m-K), and ChemicalVapor Deposited (CVD) graphene (about 5000 W/m-K). The acceptor waferinterconnects may be substantially surrounded by BEOL isolation 3196.The heat removal apparatus, which may include acceptor wafer heat sink3197, may include an external surface from which heat transfer may takeplace by methods such as air cooling, liquid cooling, or attachment toanother heat sink or heat spreader structure.

Furthermore, some or all of the layers utilized as shield/heat sinklayer 3188, which may include shapes of material such as the strips orfingers as illustrated in FIG. 27B-1 , may be driven by a portion of thesecond layer transistors and circuits (within the transferred donorwafer layer or layers) or the acceptor wafer transistors and circuits,to provide a programmable back-bias to at least a portion of the secondlayer transistors. The programmable back bias may utilize a circuit todo so, for example, such as shown in FIG. 17B of U.S. Pat. No.8,273,610, the contents incorporated herein by reference; wherein the‘Primary’ layer may be the second layer of transistors for which theback-bias is being provided, the ‘Foundation’ layer could be either thesecond layer transistors (donor) or first layer transistors (acceptor),and the routing metal lines connections 1723 and 1724 may includeportions of the shield/heat sink layer 3188 layer or layers. Moreover,some or all of the layers utilized as shield/heat sink layer 3188, whichmay include strips or fingers as illustrated in FIG. 27B-1 , may bedriven by a portion of the second layer transistors and circuits (withinthe transferred donor wafer layer or layers) or the acceptor wafertransistors and circuits to provide a programmable power supply to atleast a portion of the second layer transistors. The programmable powersupply may utilize a circuit to do so, for example, such as shown inFIG. 17C of U.S. Pat. No. 8,273,610, the contents incorporated herein byreference; wherein the ‘Primary’ layer may be the second layer oftransistors for which the programmable power supplies are being providedto, the ‘Foundation’ layer could be either the second layer transistors(donor) or first layer transistors (acceptor), and the routing metalline connections from Vout to the various second layer transistors mayinclude portions of the shield/heat sink layer 3188 layer or layers. TheVsupply on line 17C12 and the control signals on control line 17C16 maybe controlled by and/or generated in the second layer transistors (forexample donor wafer device structures such as the JFETs or JLTs formedas described in relation to FIG. 31 ) or first layer transistors(acceptor, for example acceptor wafer transistors and devices 3193), oroff chip circuits. Furthermore, some or all of the layers utilized asshield/heat sink layer 3188, which may include strips or fingers asillustrated in FIG. 27B-1 or other shapes such as those in FIG. 27B, maybe utilized to distribute independent power supplies to various portionsof the second layer transistors (for example donor wafer devicestructures such as the JFETs or JLTs formed as described in relation toFIG. 31 ) or first layer transistors (acceptor, for example acceptorwafer transistors and devices 3193) and circuits; for example, one powersupply and/or voltage may be routed to the sequential logic circuits ofthe second layer and a different power supply and/or voltage routed tothe combinatorial logic circuits of the second layer. Moreover, thepower distribution circuits/grid may be designed so that Vdd may have adifferent value for each stack layer. Patterning of shield/heat sinklayer 3188 or layers can impact their heat-shielding capacity. Thisimpact may be mitigated, for example, by enhancing the top shield/heatsink layer 3188 areal density, creating more of the secondaryshield/heat sink layers 3188, or attending to special CAD rulesregarding their metal density, similar to CAD rules that are required toaccommodate Chemical-Mechanical Planarization (CMP). These constraintswould be integrated into a design and layout EDA tool. Moreover, thesecond layer of circuits and transistors, for example, for example donorwafer device structures such as the JFETs or JLTs formed as described inrelation to FIG. 31 , may include I/O logic devices, such as SerDes(Serialiser/Deserialiser), and conductive bond pads (not shown) (hereinsuch as FIG. 33 ). The output or input conductive pads of the I/Ocircuits may be coupled, for example by bonded wires, to externaldevices. The output or input conductive pads may also act as a contactport for the 3D device output to connect to external devices. The emfgenerated by the I/O circuits could be shielded from the other layers inthe stack by use of, for example, the shield/heat sink layer 3188.Placement of the I/O circuits on the same stack layer as the conductivebond pad may enable close coupling of the desired I/O energy and lowersignal loss. Furthermore, the second layer of circuits and transistors,for example donor wafer device structures such as the JFETs or JLTsformed as described in relation to FIG. 31 , may include RF (RadioFrequency) circuits and/or at least one antenna. For example, the secondlayer of circuits and transistors may include RF circuits to enable anoff-chip communication capability to external devices, for example, awireless communication circuit or circuits such as a Bluetooth protocolor capacitive coupling. The emf generated by the RF circuits could beshielded from the other layers in the stack by use of, for example, theshield/heat sink layer 3188

TLVs 3160 may be formed through the transferred layers. As thetransferred layers may be thin, on the order of about 200 nm or less inthickness, the TLVs may be easily manufactured as a typical metal tometal via may be, and said TLV may have state of the art diameters suchas nanometers or tens to a few hundreds of nanometers, such as, forexample about 150 nm or about 100 nm or about 50 nm. The thinner thetransferred layers, the smaller the thru layer via diameter obtainable,which may result from maintaining manufacturable via aspect ratios. Thethickness of the layer or layers transferred according to someembodiments of the invention may be designed as such to match and enablethe most suitable obtainable lithographic resolution (and enable the useof conventional state of the art lithographic tools), such as, forexample, less than about 10 nm, 14 nm, 22 nm or 28 nm linewidthresolution and alignment capability, such as, for example, less thanabout 5 nm, 10 nm, 20 nm, or 40 nm alignment accuracy/precision/error,of the manufacturing process employed to create the thru layer vias orany other structures on the transferred layer or layers.

Formation of CMOS, such as for the described JFETs or JLTs, in onetransferred layer and the orthogonal connect strip methodology may befound as illustrated in at least FIGS. 30-33, 73-80, and 94 and relatedspecification sections of U.S. Pat. No. 8,273,610, and may be applied toat least the FIG. 31 formation techniques herein. Transferred layer orlayers may have regions of STI or other transistor elements within it oron it when transferred, but would then use alignment and connectionschemes for layer transfer of patterned layers as described inincorporated patent references.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 31A through 31G are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations are possible such as, for example, a p-channel JFET or JLTmay be formed with changing the types of dopings appropriately.Moreover, the N− substrate donor wafer 3100 may be p type or un-doped.Furthermore, isolation regions 3105 may be formed by a hard mask definedprocess flow, wherein a hard mask stack, such as, for example, siliconoxide and silicon nitride layers, or silicon oxide and amorphous carbonlayers, may be utilized. Moreover, CMOS JFETs or JLTs may be constructedwith n-JFETs or JLTs in a first mono-crystalline silicon layer andp-JFETs or JLTs in a second mono-crystalline layer, which may includedifferent crystalline orientations of the mono-crystalline siliconlayers, such as for example, <100>, <111> or <551>, and may includedifferent contact silicides for optimum contact resistance to p or ntype source, drains, and gates. Further, dopant segregation techniques(DST) may be utilized to efficiently modulate the source and drainSchottky barrier height for both p and n type junctions formed.Furthermore, raised source and drain contact structures, such as etchand epi SiGe and SiC, may be utilized for strain and contact resistanceimprovements and the damage from the processes may be opticallyannealed. Back gated and/or multi Vt JFETs or JLTs may be constructedutilizing the inventive concepts in FIGS. 30A-30G herein. Many othermodifications within the scope of the invention will suggest themselvesto such skilled persons after reading this specification. Thus theinvention is to be limited only by the appended claims.

An embodiment of the invention may include an exemplary partiallyprocessed 3D device with substrate being processed with topsideillumination as illustrated in FIG. 32 . The topside illumination 3299may be an optical anneal for purposes, such as, for example, dopantannealing, STI densification and annealing, silicidation, and/or ion-cutdamage repair, which have been described at least herein and inincorporated patents and patent publications. Furthermore, topsideillumination 3299 may be an optical anneal that is die sized, or reticlesized, or other size and shape as has been described at least herein andin incorporated patents and patent publications. A transferred layer3203, which may be a transferred layer or layers as described at leastherein and in incorporated patents and patent publications, may havebeen transferred and bonded to an acceptor wafer or substrate, and mayinclude bonding at the interface between donor bonding oxide 3280 andacceptor bonding oxide 3281. Transferred layer 3203 may have a protectlayer 3266 (or region) atop it, which may function as a opticalabsorber, reflector, or energy spreader as described in at least hereinand in incorporated patents and patent publications, and may remain apart of the device at the end of device processing or be sacrificial(removed). Transferred layer 3203 may include its entirety or portions,isotopically enriched silicon (such as, for example, >99% ²⁸Si) orgermanium to enable a greater heat conductivity. The relatively highercost of the isotopically enriched layer or regions can be mitigated bythe reuse of a donor wafer comprised wholly or partially with thematerial. The acceptor wafer at the time of bonding to the donor waferand at exposure to topside illumination 3299 may include acceptorbonding oxide 3281, top shield layer 3285, inter-shield insulator layer3298, bottom shield layer 3288, second inter-shield insulator layer3296, eight ‘2×’ interconnect layers 3283 that may be interspersed withfour ‘2×’ insulator layers 3294, a ‘1×’ interconnect layer 3287, a ‘1×’insulator layer 3292, device die thermal conduction paths 3245, devicescribe-lane thermal conduction paths 3246, second device die thermalconduction paths 3244, second device scribe-lane thermal conductionpaths 3247, and a base wafer with transistors and circuits 3295. Theacceptor wafer may have another combination of these layers and regionsas would be clear to one skilled in the art. The elements of theexemplary acceptor wafer may include the materials, process flows,construction, use, etc. as has been described herein and in incorporatedpatents and patent publications, for example, transferred layer 3203 maybe doped or undoped silicon, and may have regions of STI or othertransistor elements within it or on it, and may include multiple layersor regions of doping. Moreover, transferred layer 3203 may includelayers or regions that have materials with melting points higher than900° C. (for example doped mono-crystalline silicon or polysilicon oramorphous silicon, tungsten, tantalum nitride) that may be used, forexample, as a back-bias or body bias region or layer, as has beendescribed herein and in incorporated patents and patent publications.Top shield layer 3285 may have layered shield regions wherein thehorizontal thermal conduction is substantially greater than the verticalheat conduction. The bonded stack of the acceptor wafer and transferredlayers may include scribe regions 3265, either preformed and/orpredetermined scribelanes and/or dicelines, or may include customfunction definition and etching, or a combination of both. Scriberegions 3265 may be constructed with device scribe-lane thermalconduction paths 3246 that may provide a thermal conduction path fromthe top shield layer 3285 to the base wafer with transistors andcircuits 3295, which could then conduct heat that may be generated fromtopside illumination 3299 to the illumination machine heat sink/chuck3240 and thus help prevent damage from the topside illumination 3299 ofthe acceptor interconnect layers, such as, for example, the eight ‘2×’interconnect layers 3283, four ‘2×’ insulator layers 3294, 1×’interconnect layer 3287, ‘1×’ insulator layer 3292, and the transistorsand circuits of base wafer with transistors and circuits 3295. Seconddevice scribe-lane thermal conduction paths 3247 may thermally conductfrom bottom shield layer 3288 to the base wafer with transistors andcircuits 3295 and the illumination machine heat sink/chuck 3240. Devicedie thermal conduction paths 3245 within the device die, may provide athermal conduction path from the top shield layer 3285 to the base waferwith transistors and circuits 3295, which could then conduct heat thatmay be generated from topside illumination 3299 to the illuminationmachine heat sink/chuck 3240 and thus help prevent damage from thetopside illumination 3299 of the acceptor interconnect layers, such as,for example, the eight ‘2×’ interconnect layers 3283, four ‘2×’insulator layers 3294, 1×’ interconnect layer 3287, ‘1×’ insulator layer3292, and the transistors and circuits of base wafer with transistorsand circuits 3295, and has been described herein and in incorporatedpatents and patent publications. Second device die thermal conductionpaths 3244 may thermally conduct from bottom shield layer 3288 to thebase wafer with transistors and circuits 3295 and the illuminationmachine heat sink/chuck 3240. Device scribe-lane thermal conductionpaths 3246 may be removed in the later dice singulation processeswhereas the device die thermal conduction paths 3245 may remain in thefinished device and provide cooling of the second layer and abovetransistor and circuit layers when the device is in operation andgenerating heat from the device operation. The density of device diethermal conduction paths 3245, device scribe-lane thermal conductionpaths 3246, second device die thermal conduction paths 3244, and seconddevice scribe-lane thermal conduction paths 3247 is a device design andthermal architecture calculation, but may be on the order of 1 every 100um² (Wei H., et al., “Cooling Three-Dimensional Integrated CircuitsUsing Power Delivery Networks”, IEDM 2012, 14.2, December 2012.incorporated by reference in entirety). Scribelanes (or dicelanes), suchas scribe regions 3265, may be 10 um wide, 20 um wide, 50 um wide 100 umwide, or greater than 100 um wide depending on design choice and diesingulation process capability.

Persons of ordinary skill in the art will appreciate that theillustrations in FIG. 32 are exemplary and are not drawn to scale. Suchskilled persons will further appreciate that many variations may bepossible such as, for example, bottom shield layer 3288 may also beformed as a layered shield/heat sink layer or region. Moreover, althoughmany of the elements in the FIG. 32 may be called layers, they maininclude within them regions. Furthermore, device scribe-lane thermalconduction paths 3246 and device die thermal conduction paths 3245 maybe formed so that there is no electrical connection to bottom shieldlayer 3288, unless they are designed to do so as the same circuit node.Further, the choice of eight ‘2×’ interconnect layers 3283 that may beinterspersed with four ‘2×’ insulator layers 3294, a ‘1×’ interconnectlayer 3287, a ‘1×’ insulator layer 3292 is a design choice and may bedifferent according to the design considerations, both devicefunctionally and thermally. Moreover, the various semiconductor layerswithin the 3D device may have various circuitry, functions andconnection, for example, as described herein (such as FIG. 33 ) or inincorporated patent references. Thus the invention is to be limited onlyby the appended claims.

The various layers of a 3D device may include many types of circuitry,which may be formed by regions of transistors and other semiconductordevice elements within that layer or in combination with other layers ofthe 3D device, and connections between the transistors within the sameregion, region to region and vertically (layer to layer) may be providedby layers of interconnect metallization and vertical connections such asTLVs and TSVs. In addition, power routing within the 3D device mayutilize thicker and more conductive interconnect metallization thananother layer, especially if the layer is closest to the source ofexternal power and/or has a greater current load/supply requirement.Many individual device and interconnect embodiments for 3D devices havebeen described herein and in the incorporated patent references. Asillustrated in FIG. 33 , some additional embodiments and combinations(further embodiments) of devices, circuits, paths, and connections aredescribed and may utilize similar materials, constructions and methodsas the incorporated references or discussed herein. With reference toembodiments described herein, for example with respect to FIGS. 30A-30Gherein, and in the incorporated patent references, a substrate layer,which may have a thicker body than other semiconductor layers above orwithin the 3D device, such as acceptor 3310 may be formed and mayinclude heat sink 3397, acceptor substrate 3395, acceptor wafertransistors and circuits 3393, first (acceptor) layer metal interconnect3381 which may include first layer contacts 3391, first layer vias 3383,at least one shield layer/region 3388 (two layers and many regions, suchas lower level shield layer region 3385, shown), interconnect insulatorregions 3396 and ESD diode structures 3307. A second semiconductor layermay be transferred and constructed on top of the first layer withisolation layer 3380 in-between and vertical layer to layerinterconnections may be provided by TLV/TSV 3335, only one is shown. Alayer of transistors and circuits 3322 may include second layer inputdevice structures 3376, FD ESD structures 3317, Phase Lock Loop circuitsPLL 3318, SERDES circuitry 3319, and output device structure 3351.Second interconnections layer 3330 may include at least onelayer/regions of metallization and associated contacts and via, forexample, second layer metallization M1 segments 3328, 3321, 3323, 3325,second layer contacts 3326, second layer vias 3352, and conductive pads3390. The 3D device may be connected to external devices utilizing manystructures known to those skilled in the art, for example, bond wires3399. Input device structures 3376 and output device structure 3351 maybe connected to external devices through, for example, second layercontacts 3326, second layer metallization M1 segments 3328, second layervias 3352, conductive pads 3390, and bond wires 3399. A portion of thetransistors within input device structures 3376 and output devicestructure 3351 may be larger in either or both width and length thanmost transistors within acceptor wafer transistors and circuits 3393.Input device structures 3376 (and output device structure 3351) may besubjected to voltage and/or current transients from external devices orgenerated externally and traveling to the 3D device along bond wires3399. Input device structures 3376 (and output device structure 3351)may be protected by dissipating the transient energy in diodestructures, such as ESD diode structures 3307 on the relatively thicker(than for example, the second semiconductor layer) acceptor substrate3395, which may be connected by a multiplicity of connection stacks suchas first (acceptor) layer metal interconnect 3381 which may includefirst layer contacts 3391, first layer vias 3383, at least one shieldlayer/region 3388, TLV/TSV 3335, and second layer metallization M1segments 3328. Input device structures 3376 (and output device structure3351) may be protected by dissipating the transient energy in atransient filtering circuitry such as for example, FD ESD structures3317, which may reside on a relatively thin semiconductor layer in the3D device and may effectively utilize fully depleted transistors in thefilter circuitry. FD ESD structures 3317 may be coupled to input devicestructures 3376 (and output device structure 3351) by second layerinterconnections (not shown). Input device structures 3376 may beconnected to PLL 3318, for example, thru second layer metallization M1segment 3321 and second layer contacts 3326. Input device structures3376 may be connected to SERDES circuitry 3319, for example, thru secondlayer metallization (not shown). Output device structures 3351 may beconnected to SERDES circuitry 3319, for example, thru second layermetallization M1 segment 3323 and second layer contacts 3326. Outputdevice structures 3351 may drive signals thru the connection toconductive pads 3390 and then out to external devices thru bond wires3399. Transistors within a lower layer, for example within acceptorwafer transistors and circuits 3393, may be connected (not shown) to theoutput device structure 3351 and drive a signal to the output devicestructure 3351, and a portion of the transistors of output devicestructure 3351 may have a larger width and/or length than thetransistors within acceptor wafer transistors and circuits 3393. Powerfrom external sources may be routed thru bond wires 3399 to conductivepads 3390 to the 3D device, wherein at least a portion of the secondinterconnections layer 3330 may be constructed with thicker and/or widermetallization wiring (for example 4× wiring as described in incorporatedpatent references) so to provide the higher current carrying capabilityrequired for the second layer power distribution grid/network than thatof the lower layer, in this example, first layer metallization wiring(for example 1× or 2× wiring as described in incorporated patentreferences). The width and/or length of the transistors of the secondlayer of transistors and circuits 3322, for example a portion of thosein second layer input device structures 3376 and/or FD ESD structures3317 and/or output device structures 3351, may be substantially largerthan the width and/or length of transistors in acceptor wafertransistors and circuits 3393.

Persons of ordinary skill in the art will appreciate that theillustrations in FIG. 33 are exemplary and are not drawn to scale. Suchskilled persons will further appreciate that many variations may bepossible such as, for example, a thick enough semiconductor layer toenable ESD diode style protection circuitry to be constructed need notonly be on the base or substrate layer, but may reside elsewhere in the3D device stack. Moreover, the output circuitry including output devicestructures 3351 may wholly or partially reside on a semiconductortransistor layer that is not on top, and vertical connections includingTLVs/TSV may be utilized to connect the output device structures 3351 toconductive pads 3390. Furthermore, the input circuitry including inputdevice structures 3376 may wholly or partially reside on a semiconductortransistor layer that is not on top, and vertical connections includingTLVs/TSV may be utilized to connect the input device structures 3376 toconductive pads 3390. Similarly, SERDES circuitry and 3319 PLL 3318 maywholly or partially reside on a semiconductor transistor layer that isnot on top, three choices being one of design choice and devicecharacteristics driven. Furthermore, connection to external devices(signal and/or power supply) may be made on the backside of acceptorsubstrate 3395. Moreover, connection to external devices form the 3Ddevice may utilize many types of structures other than bond wires 3399shown in the illustration, for example, flipchip and bumps, wirelesscircuitry. Thus the invention is to be limited only by the appendedclaims.

Some embodiments of the invention may include alternative techniques tobuild IC (Integrated Circuit) devices including techniques and methodsto construct 3D IC systems. Some embodiments of the invention may enabledevice solutions with far less power consumption than prior art. Thedevice solutions could be very useful for the growing application ofmobile electronic devices and mobile systems such as, for example,mobile phones, smart phone, and cameras, those mobile systems may alsoconnect to the internet. For example, incorporating the 3D ICsemiconductor devices according to some embodiments of the inventionwithin the mobile electronic devices and mobile systems could providesuperior mobile units that could operate much more efficiently and for amuch longer time than with prior art technology.

Smart mobile systems may be greatly enhanced by complex electronics at alimited power budget. The 3D technology described in the multipleembodiments of the invention would allow the construction of low powerhigh complexity mobile electronic systems. For example, it would bepossible to integrate into a small form function a complex logic circuitwith high density high speed memory utilizing some of the 3D DRAMembodiments of the invention and add some non-volatile 3D NAND chargetrap or RRAM described in some embodiments of the invention. Mobilesystem applications of the 3DIC technology described herein may be foundat least in FIG. 156 of U.S. Pat. No. 8,273,610, the contents of whichare incorporated by reference.

In this document, the connection made between layers of, generallysingle crystal, transistors, which may be variously named for example asthermal contacts and vias, Thru Layer Via (TLV), TSV (Thru Silicon Via),may be made and include electrically and thermally conducting materialor may be made and include an electrically non-conducting but thermallyconducting material or materials. A device or method may includeformation of both of these types of connections, or just one type. Byvarying the size, number, composition, placement, shape, or depth ofthese connection structures, the coefficient of thermal expansionexhibited by a layer or layers may be tailored to a desired value. Forexample, the coefficient of thermal expansion of the second layer oftransistors may be tailored to substantially match the coefficient ofthermal expansion of the first layer, or base layer of transistors,which may include its (first layer) interconnect layers.

Base wafers or substrates, or acceptor wafers or substrates, or targetwafers substrates herein may be substantially comprised of a crystallinematerial, for example, mono-crystalline silicon or germanium, or may bean engineered substrate/wafer such as, for example, an SOI (Silicon onInsulator) wafer or GeOI (Germanium on Insulator) substrate.

It will also be appreciated by persons of ordinary skill in the art thatthe invention is not limited to what has been particularly shown anddescribed hereinabove. For example, drawings or illustrations may notshow nor p wells for clarity in illustration. Moreover, transistorchannels illustrated or discussed herein may include dopedsemiconductors, but may instead include undoped semiconductor material.Further, any transferred layer or donor substrate or wafer preparationillustrated or discussed herein may include one or more undoped regionsor layers of semiconductor material. Moreover, epitaxial regrow ofsource and drains may utilize processes such as liquid phase epitaxialregrowth or solid phase epitaxial regrowth, and may utilize flash orlaser processes to freeze dopant profiles in place and may also permitnon-equilibrium enhanced activation (superactivation). Further,transferred layer or layers may have regions of STI or other transistorelements within it or on it when transferred. Rather, the scope of theinvention includes both combinations and sub-combinations of the variousfeatures described hereinabove as well as modifications and variationswhich would occur to such skilled persons upon reading the foregoingdescription. Thus the invention is to be limited only by the appendedclaims.

We claim:
 1. A method for producing a 3D semiconductor device, themethod comprising: providing a first level, said first level comprisinga first single crystal layer; forming control circuitry in and/or onsaid first level, wherein said control circuitry comprises first singlecrystal transistors; forming a first metal layer above said first singlecrystal layer; forming a second metal layer above said first metallayer; forming a third metal layer above said second metal layer;forming at least one second level disposed on top of or above said thirdmetal layer; performing additional processing steps to form a pluralityof second transistors within said at least one second level; forming afourth metal layer above said at least one second level; and forming afifth metal layer above said fourth metal layer, wherein said at leastone second level comprises at least one first oxide layer overlaid by atransistor layer and then overlaid by second oxide layer, wherein adistance from a top of said first oxide layer to a bottom of said secondoxide layer is less than two microns, wherein said device comprises aglobal power distribution grid, wherein said global power distributiongrid comprises said fifth metal layer, wherein said device comprises alocal power distribution grid, wherein said local power distributiongrid comprises said second metal layer, and wherein said fifth metallayer thickness is at least 50% greater than said second metal layerthickness.
 2. The method according to claim 1, wherein at least one ofsaid plurality of second transistors comprises a metal gate.
 3. Themethod according to claim 1, further comprising: a step of replacing asecond transistor gate with a metal gate.
 4. The method according toclaim 1, wherein said second metal layer thickness is at least 50%greater than said third metal layer thickness.
 5. The method accordingto claim 1, wherein said fifth metal layer is aligned to said firstmetal layer with a less than 40 nm alignment error.
 6. The methodaccording to claim 1, further comprising: forming a third level disposedbetween said second level and said fourth metal layer, wherein saidthird level comprises a plurality of third transistors.
 7. The methodaccording to claim 1, wherein said form a plurality of secondtransistors comprises use of Atomic Layer Deposition (ALD).
 8. A methodfor producing a 3D semiconductor device, the method comprising:providing a first level, said first level comprising a first singlecrystal layer; forming a plurality of first transistors in and/or onsaid first level; forming a first metal layer above said first singlecrystal layer; forming a second metal layer above said first metallayer; forming a third metal layer above said second metal layer;forming at least one second level disposed on top of or above said thirdmetal layer; performing a first etch step; performing additionalprocessing steps to form a plurality of second transistors in and/or onsaid at least one second level; forming a fourth metal layer above saidat least one second level; forming a connection to said at least onesecond metal layer from said fourth metal layer, wherein said at leastone second level comprises at least a first oxide layer overlaid by atransistor layer and overlaid by a second oxide layer, wherein thedistance from said first oxide layer to said second oxide layer is lessthan two microns, wherein said connection comprises a via through saidat least one second level; and forming a fifth metal layer above saidfourth metal layer, wherein said via comprises a radius of less than 450nm, wherein said device comprises a global power distribution grid,wherein said global power distribution grid comprises said fifth metallayer, wherein said device comprises a local power distribution grid,wherein said local power distribution grid comprises said second metallayer, and wherein said fifth metal layer thickness is at least 50%greater than said second metal layer thickness.
 9. The method accordingto claim 8, wherein at least one of said plurality of second transistorscomprises a metal gate.
 10. The method according to claim 8, furthercomprising: a step of replacing at least one gate of said plurality ofsecond transistors with a metal gate.
 11. The method according to claim8, wherein said second metal layer thickness is at least 50% greaterthan said third metal layer thickness.
 12. The method according to claim8, wherein said fifth metal layer is aligned to said first metal layerwith a less than 40 nm alignment error.
 13. The method according toclaim 8, further comprising: forming a third level disposed between saidat least one second level and said fourth metal layer, wherein saidthird level comprises a plurality of third transistors.
 14. The methodaccording to claim 8, wherein said form a plurality of secondtransistors comprises use of Atomic Layer Deposition (ALD).
 15. A methodfor producing a 3D semiconductor device, the method comprising:providing a first level, said first level comprising a first singlecrystal layer; forming a plurality of first transistors in and/or onsaid first level; forming a first metal layer above said first singlecrystal layer; forming a second metal layer above said first metallayer; forming a third metal layer above said second metal layer;forming at least one second level disposed on top of or above said thirdmetal layer; performing additional processing steps to form a pluralityof second transistors within said at least one second level; forming afourth metal layer above said at least one second level; forming aconnection to said second metal layer from said fourth metal layer,wherein said connection comprises a via through said at least one secondlevel; and forming a fifth metal layer above said fourth metal layer,wherein said at least one second level comprises at least a first oxidelayer overlaid by a transistor layer and overlaid by a second oxidelayer, wherein the distance from said first oxide layer to said secondoxide layer is less than two microns, wherein at least one of saidplurality of second transistors comprises a metal gate, and wherein saidfifth metal layer thickness is at least 50% greater than said secondmetal layer thickness.
 16. The method according to claim 15, furthercomprising: a step of replacing gates of said plurality of secondtransistors with metal gates.
 17. The method according to claim 15,wherein said second metal layer thickness is at least 50% greater thansaid third metal layer thickness.
 18. The method according to claim 15,wherein said via comprises a radius of less than 450 nm.
 19. The methodaccording to claim 15, further comprising: forming a third leveldisposed between said at least one second level and said fourth metallayer, wherein said third level comprises a plurality of thirdtransistors.
 20. The method according to claim 15, wherein said metalgate comprises tungsten.